LPSO/MFS2022
The 5th International Symposium on
Long-Period Stacking/Order Structure and Mille-feuille Structure

11-14 December, 2022
Prince Hotel SHINAGAWA, JAPANhttp://www.mfs-materials.jp

Table of contents
Preface ................................................................................................................ 2
Committees & Invited speakers ................................................................................. 3-4
Schedule & Floor map ............................................................................................... 6-7
Program .................................................................................................................... 8-16
AbstractOral
1st session ......................................................................................................... 18-25
2nd session ........................................................................................................ 26-31
3rd session ......................................................................................................... 32-38
4th session ......................................................................................................... 39-47
5th session ......................................................................................................... 48-54
6th session ......................................................................................................... 55-61
7th session ......................................................................................................... 62-68
PosterStudents ............................................................................................................ 70-93
Researcher ...................................................................................................... 94-107

Preface
We warmly invite you to the 5th International Symposium on Long-Period
Stacking/Order and Mille-feuille Structures “LPSO/MFS 2022” to be held in Tokyo on
11 – 14 December 2022.
The LPSO/MFS 2022 serves to share rapid developments of layer-structured LPSO/MFS
Mg alloys, which reveal remarkable strength through unique kink-type deformations. The
symposium primary aims to provide a platform for those working in these materials topresent their most recent research findings. Furthermore, the symposium will provide an
opportunity to spark frontier ideas, which encourage extending the LPSO/MFS concept
to various materials, including light alloys (Al, Ti, etc.), ceramics and even polymer
materials.
The scientific scope of LPSO/MFS 2022 will cover all important aspects of a layerstructure design and/or kink-type deformations in high-strength structural materials, bothfor experiments and theory in the field of materials science, structural science, mechanics,
computer simulations and mathematical modeling.
We heartily welcome you to Tokyo to participate in the Symposium along with yourstudents, postdocs, colleagues, and others. Please mark the conference dates in yourcalendar NOW!
Eiji Abe and Yoshihito Kawamura
Chairpersons
LPSO/MFS 2022

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Committee
Chair
Eiji Abe, University of Tokyo
Yoshihito Kawamura, Kumamoto University

Organizing Committee
Michiaki Yamasaki, Kumamoto University
Yoshihito Kawamura, Kumamoto University
Hidetoshi Somekawa, National Institute for Materials Science
Koji Hagihara, Nagoya Institute of Technology
Eiji Abe, University of Tokyo
Hajime Kimizuka, Nagoya University
Toshiyuki Fujii, Tokyo Institute of Technology
Hideharu Nakashima, Kyushu University
Seiji Miura, Hokkaido University
Hiromu Saito, Tokyo University of Agriculture and Technology
Hiroshi Ito, Yamagata University

Local Committee
Eiji Abe, University of Tokyo
Toshiyuki Fujii, Tokyo Institute of Technology
Yuri Shinohara, Tokyo Institute of Technology
Tomotaka Miyazawa, Tokyo Institute of Technology
Daisuke Egusa, University of Tokyo-3-

Invited speakers
Keynote speakers
Prof. Eiji Abe University of Tokyo
Prof. Yoshihito Kawamura MRC, Kumamoto University
Prof. Michel W. Barsoum Drexel University
Prof. Jian-Feng Nie Monash University
Prof. Alexey Romanov ITMO University
Prof. Sean R. Agnew University of Virginia

Invited speakers
Prof. Koji Hagihara Nagoya Institute of Technology
Dr. Hidetoshi Somekawa National Institute for Materials Science
Dr. Koji Kimura Nagoya Institute of Technology
Prof. Ken-ichi IKEDA Hokkaido University
Prof. Hajime Kimizuka Nagoya University
Prof. Gerardo GARCES CENIM-CSIC
Prof. Kristian Mathis Charles University, Faculty of Mathematics and Physics
Prof. Liangbin Li University of Science and Technology of China
Prof. Hiromu Saito Tokyo University of Agriculture and Technology
Prof. Masatoshi Tokita Tokyo Institute of Technology
Prof. Hiroshi Ito Yamagata University
Dr. Daisuke Egusa University of Tokyo
Dr. Daria Drozdenko Charles University
Prof. Michiaki Yamasaki Kumamoto University
Prof. Xiaohong Shao Chinese Academy of Sciences
Dr. Toko Tokunaga Nagoya Institute of Technology

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LPSO/MFS2022 Schedule-6-

SHINAGAWA PRINCE HOTEL Floor map-7-

The 5th International Symposium on
Long-Period Stacking/Order Structure and Mille-feuille Structure
Program
December 12 (Mon.), 2022
1st session: 9:00 ~ 12:00
Chair: Prof. M. W. Barsoum & Prof. T. Fujii
9:00~9:30 Keynote“Mille-Feuille Structured Alloys/Ceramics/Polymers: Present Status and Future Perspectives”
Prof. E. Abe
University of Tokyo

9:30~10:00 Keynote“Production and Kink Strengthening of MFS-type Mg-Zn-Y Alloy with a-Mg Single Phase”
Prof. Y. Kawamura
MRC, Kumamoto University

10:00~10:25 Invite“Kink-band formation in mille-feuille structured metallic materials prepared by directional
solidification”
Prof. K. Hagihara
Nagoya Institute of Technology

10:25~10:50 Invite“Kink boundary formation and morphology in wrought-processed Mg-Y-Zn alloys”
Dr. H. Somekawa
National Institute for Materials Science

10:50~11:15 Invite“Self-Tuned Structure of Solute-Clusters in Dilute Mg-Zn-Y Alloy Revealed by X-ray Fluorescence
Holography”
Dr. K. Kimura
Nagoya Institute of Technology

11:15~11:30 Oral

“Direct observation of pseudo-gap electronic structure in the Mg-Zn-Y alloys studied byhard X-ray photoelectron spectroscopy”
Prof. H. Miyazaki
Nagoya Institute of Technology

11:30~11:45 Oral

“Temperature and strain dependence of plastic deformation behavior of long-period
stacking-ordered magnesium alloys”
Dr. T. Miyazawa
Tokyo Institute of Technology

11:45~12:00 Oral

“Microstructure and hardness in Mg-Y-Zn alloys with long-periodic stacking ordered phaseprocessed by equal-channel-angular extrusion”
Prof. M. Yuasa
Doshisha University

Lunch: 12:00 ~ 13:30
2nd session: 13:30 ~ 15:35
13:30~14:00 Keynote

Chair: Prof. K. Mathis & Prof. K. Hagihara“Ripplocations: A Universal Deformation Mechanism in Millefeuile Solids”
Prof. M. W. Barsoum
Drexel University-8-

14:00~14:25 Invite“Effects of Kink Boundaries on High Temperature Deformation Behavior of Textured Ti3SiC2 MAX
Phase Sintered Body”
Prof. K. Ikeda
Hokkaido University

14:25~14:50 Invite“Atomistic analysis of microscopic mechanisms of kink formation in metallic and ceramic mille-feuillestructures”
Prof. H. Kimizuka
Nagoya University

14:50~15:05 Oral

“Kink Strengthening in TiNi-Nb and TiCo-Nb Alloys with Eutectic Mille-feuille Structure”
Prof. K. Ishikawa
Kanazawa University

15:05~15:20 Oral

“Plasticity enhanced in kinking orientations of cubic-structured ceramics micropillars”
Dr. H. Masuda
University of Tokyo

15:20~15:35 Oral

“Nanoindentation Examination of Kink Boundary Hardness in Ti3SiC2 MAX Phase”
National Institute for Materials Science
Dr. K. Morita

Coffee break
3rd session: 16:05 ~ 18:10
16:05~16:35 Keynote

Chair: Dr. D. Drozdenko & Prof. M. Yamasaki“Microstructure, Deformation and Property of Wrought Magnesium Alloys”
Prof. J. F. Nie
Monash University

16:35~17:00 Invite“Tensile and compressive mechanical behaviour in fully-lamellar extruded MgGd2Zn1 alloy”
Prof. G. Garces
CENIM-CSIC

17:00~17:25 Invite“Hot deformation of Mg-Y-Zn alloy with different content of the LPSO phase studied by in-situ
synchrotron radiation diffraction”
Prof. K. Mathis
Charles University

17:25~17:40 Oral

“Monitoring of strengthening of LPSO in αMg/LPSO dual phase alloy by hot-extrusion
using in situ neutron diffraction during deformation”
Dr. S. Harjo
Japan Atomic Energy Agency

17:40~17:55 Oral

“Kink strengthening of LPSO Mg-Zn-Y alloys after processing by high-pressure sliding (HPS)”
Dr. Y. Tang
Kyushu Institute of Technology

17:55~18:10 Oral

“Texture evolution and mechanical properties of Mg-9Y-6Zn alloy via vortex extrusion”
Prof. D. Ando
Tohoku University-9-

December 13 (Tue.), 2022
Excursion 12/13 8:00 ~ 13:00
Tour around Imperial Palace & Sennsoji Temple (Asakusa)
4th session: 13:30 ~ 15:55 Chair: Prof. H. Ito & Prof. H. Saito
13:30~13:55 Invite (Online)“Stretch-induced structural evolution of semicrystalline polymers: the effects of strain rate”
Prof. L. Li
University of Science and Technology of China

13:55~14:20 Invite“Deformation Behavior of High-strength Mille-feuille Structured PVDF”
Prof. H. Saito
Tokyo University of Agriculture and Technology

14:20~14:45 Invite“Effect of Smectic Layer Deformation on Mechanical Properties of Glassy Liquid Crystal Polymer Fibers”
Prof. M. Tokita
Tokyo Institute of Technology

14:45~15:10 Invite“Preparation and Mechanical Properties Evaluation of Multilayer Film having Mille-feuille and Kink
Structures”
Yamagata University
Prof. H. Ito

15:10~15:25 Oral

“Large-scale MD simulations of reinforced polyethylene crystals by pre-elongation”
National Defense Academy
Prof. K. Hagita

15:25~15:40 Oral

“Introduction of millefeuille-like α/β layered structure and investigation of its kinkdeformation behavior in β titanium alloys”
Dr. S. Emura
National Institute for Materials Science

15:40~15:55 Oral

“Kink deformation and strengthening in an Al-30wt%Ag alloy with mille-feuille structure fabricated byaging precipitation and subsequent cold-rolling”
Prof. D. Terada
Chiba Institute of Technology

Coffee break
5th session: 16:25 ~ 18:30 Chair: Prof. J. F. Nie & Prof. T. Inamura
16:25~16:55 Keynote (Online)“Disclinations: from Theory to Practice”
Prof. A. Romanov

ITMO University

16:55~17:20 Invite“Direct observations of kink microstructure in mille-feuille structured Mg alloys”
Dr. D. Egusa
University of Tokyo

17:20~17:45 Invite“Thermal stability of the microstructure of dilute Mg alloys prepared by rapid solidified
ribbon-consolidation technique”
Dr. D. DrozdenkoCharles University-10-

17:45~18:00 Oral

“Analysis of Kink Formation Behavior in Al/Al2Cu Mille-feuille Structured Alloys”
Dr. T. Shiraiwa
University of Tokyo

18:00~18:15 Oral

“Understanding of kink-band formation by means of a rate-independent model obtained byhomogenization of mille-feuille structure”
Prof. K. Svadlenka
Kyoto University

18:15~18:30 Oral

“Modeling and Numerical Analysis of Kink Deformation based on Geometrical Elasto-Plasticity Theory”
Mr. S. H. Pranoto
Osaka University

Banquet: 19:00 ~ 21:00 @ Shinagawa Prince Hotel-11-

December 14 (Wed.), 2022
6th session: 8:30 ~ 10:10
Chair: Prof. G. Garces & Prof. H. Kimizuka
8:30~9:00 Keynote (Online)“Crystal Plasticity-Based Prediction of Forming Limit Diagrams: Application to Magnesium Alloys”
Prof. S. R. Agnew
University of Virginia

9:00~9:25 Invite“Influence of electrochemical and geometrical heterogeneities on corrosion behaviour of LPSO
phase-containing Mg-Y-Zn alloys”
Prof. M. Yamasaki
Kumamoto University

9:25~9:40 Oral

“Effects of Additional Deformation and Heat Treatment on Kink Bands on the surface of
LPSO-type Mg85Y9Zn6 Directionally Solidified Alloy Thin Plates”
Prof. M. Suzuki
Toyama Prefectural University

9:40~9:55 Oral

“Microstructure and Deformation Behavior of BCC-V/MAX two-phase alloys”
Prof. S. Miura
Hokkaido University

9:55~10:10 Oral

“Observation of as-cast and extruded Mg97Zn1Y2 alloys by neutron diffraction and thermal
dilatometer measurement”
Dr. K. Aizawa
Japan Atomic Energy Agency

Coffee break
7th session: 10:40 ~ 12:30 Chair: Dr. H. Somekawa & Prof. S. Miura
10:40~11:05 Invite (Online)“Synergetic kinking and twinning in an Mg-Zn-Y-Zr alloy with intragranular LPSO structures”
Prof. X. H. Shao
Chinese Academy of Sciences

11:05~11:30 Invite“Kink-band formation in Mg/LPSO two-phase alloys”
Dr. T. Tokunaga

11:30~11:45 Oral

Nagoya Institute of Technology“Crystal plasticity analysis of kink band formation in Mille-feuille structure”
Prof. T. Mayama
Kumamoto University

11:45~12:00 Oral

“On Scale-Free Nature of Kink Formation/Strengthening based on FTMP”
Prof. T. Hasebe
Kobe University

12:00~12:15 Oral

“Mesoscale modeling of system of planar wedge disclinations and edge dislocations via the
Airy Stress Function method”
Prof. P. Cesana
Kyushu University

12:15~12:30 Oral

“Effect of Kink Band Spacing on Kink Strengthening in LPSO-type Magnesium Alloy”
Prof. Y. Tadano
Saga University-12-Lunch: 12:30 ~ 14:00
Poster session: 14:00 ~37 posters (23 from students and 14 from researchers)
Poster Awards: 16:45 ~Closing remarks:~17:00Prof. E. Abe-13-

Poster session
Students

S-01: Toughening of the LPSO-type Mg-Zn-Y-Al RS P/M alloys
Mr. S. Nishimoto
Kumamoto University
S-02: Recrystallization Suppression and Kink Strengthening of MFS-type Mg-0.4Zn-1.0Y alloys
Mr. M. Hayashida
Kumamoto University
S-03: Investigation of fracture toughness of extruded Mg-Zn-Y alloys with multimodal
microstructure
Mr. T. Yasuda
Kumamoto University
S-04: Mechanical properties and microstructure of dilute Mg-Y-Zn alloys prepared by combinationof low cooling rate solidification and extrusion techniques
Mr. S. Ishizaki
Kumamoto University
S-05: The Effect of Hot Rolling on Kink Formation in the MFS-type Mg-0.4Zn-1.0Y Alloy with αMg Single Phase
Ms. A. Yoshida
Kumamoto University
S-06: Work-hardening Behavior of Mg-Y-Zn Alloy with Long-periodic Stacking Ordered Phasein High-pressure Torsion Process
Mr. H. Ohkoshi
Toyohashi University of Technology
S-07: Texture evolution and mechanical properties of Mg-2Y-1Zn alloy via vortex extrusion
Mr. T. Tsuji
Tohoku University
S-08: Numerical Investigation of the Microstructural Features Favoring Kink Band in Layered α/β
Ti-9Cr Alloy
Mr. J. Zhu
University of Tokyo
S-09: Deformation mechanism of LPSO-type Mg alloy after kink deformation
Mr. K. Gonome
University of Tokyo
S-10: Deformed microstructure in LPSO-type magnesium alloys exhibiting PLC effect
Mr. N. Amemiya
University of Tokyo
S-11: Dislocation analysis of solute-enriched stacking faults in kink boundaries in Mg97Zn1Y2 alloys
Mr. Y. Zhao
Kyushu University
S-12: Deformation anisotropy in hcp-Mg structure based on generalized stacking fault energy
Mr. Y. Ito
University of Tokyo-14-

S-13: Elastic energy of disclination multipole formed at intersection of kink band and shear band
Mr. R. Matsumura
Tokyo Institute of Technology
S-14: Stable Shape of Curved Ridge-Kink Consisting of a Sequence of Fine Kink-bands
Mr. X. Zhang
Tokyo Institute of Technology
S-15: Experimental Verifications of Kink-Band Strengthening in Long-Period Stacking Ordered
Mg–Zn–Y Alloy
Mr. T. Tokuzumi
Kyushu University
S-16: Deformation Behavior of Nb2Co7 as Crystal-Structure-Based Mille-feuille Structured Material
Ms. K. Yamada
Hokkaido University of Science
S-17: Orientation dependence of various properties of textured MAX phase ceramics fabricated byslip casting under strong magnetic field
Mr. J. Muraoka
Hokkaido University
S-18: Mille-feuille Structures in Al-RE Eutectic Alloys and Its Kink Formation
Mr. K. Hakita
Hokkaido University
S-19: Fabrication of Al2O3-GAP eutectic ceramics with fine anisotropic microstructure by flash
event and deformation behavior
Mr. Y. Aoki
University of Tokyo
S-20: Effect of a high-pressure press on the strength and the morphorogy of PP
Ms. Y. Ito
Yamagata University
S-21: Effect of Compression Molding of Co-Extruded PS/PBT Multilayered Film on Crystal
Structure and Mechanical Properties
Mr. A. Iwamura
University of Yamagata
S-22: Changes in the Elastomeric Mechanical Properties of Lamellae-Forming Block Copolymer
Specimens by Introduction of Kink
Ms. Y. Kokuryo
Kyoto Institute of Technology
S-23: Strengthening mechanism of crystalline polymer by heat elongation
Mr. M. Endo
University of Tokyo

Researchers

R-01: Development of hcp/bcc layered structure in Mg-Sc alloy and kink formation by compression
Dr. Y. Ogawa
National Institute for Materials Science-15-

R-02: Effect of Additional Element on Nonflammability of LPSO type Mg-Zn-Y Alloy
Dr. S. Inoue
Kumamoto University
R-03: Creep characterization of a long period stacking ordered Mg85Zn6Y9 alloy
Prof. H. Takagi
Nihon University
R-04: Observation of Kink Deformation in an LPSO Mg85Zn6Y9 Alloy using Two-directional MicroLaue Diffraction Mapping under Compression
Dr. S. Kimura
JASRI
R-05: Phase transformation behavior of LPSO structure during annealing investigated by in-situ
neutron diffraction
Dr. W. Gong
Japan Atomic Energy Agency
R-06: Development of 4D in-situ observation system for the investigation of kink development
during compression of Mg-based LPSO alloys
Dr. M. Uesugi
JASRI/SPring-8
R-07: Electronic structure of Mg-Zn-Y cluster in dilute Mg alloys studied by STEM-EELS
Prof. Y. Sato
IMRAM, Tohoku University
R-08: DFT Calculation of Kink Boundary Migration in LPSO Structure
Dr. M. Itakura
Japan Atomic Energy Agency
R-09: First-Principles Study on the Electronic Origin of Phase Stability in Mg-Zn-Y alloys with aLong-Period Stacking Order
Dr. T. Tsumuraya
Kumamoto University
R-10: Experimental Investigation on Kink Strengthening of Biotite Single Crystals: Rank-1
Connection and Surface Dislocation
Prof. H. Nagahama
Tohoku University
R-11: Shape of Local Buckling in Cu/SBS Stacking Films Subject to Compressive Deformation
Prof. Y. Kaneko
Osaka Metropolitan University
R-12: Elastic properties in a Ti3SiC2 MAX phase with a nanolayered crystal structure
Prof. M. Tane
Osaka Metropolitan University
R-13: Thermodynamic Evaluation and Experimental Investigation of Suzuki Effect in the Al–X
Binary Systems
Prof. T. Tokunaga
Kyushu Institute of Technology
R-14: Kinking in Compression of Pearlitic Steel and Resultant Plastic Anisotropy
Dr. R. Ueji
National Institute for Materials Science-16-

December 12 (Mon.)

1st ~ 3rd session-17-Mille-Feuille Structured Alloys/Ceramics/Polymers:
Present Status and Future Perspectives
Eiji AbeThe University of Tokyo, Tokyo, 113-8656, Japan*Email: abe@material.t.u-tokyo.ac.jp
In general, in structural materials design the von Mises condition has been regarded as a fundamental
necessary rule, which states that ‘there must be five independent slip systems with the relevant crystal
structure’ for continuous and stable plastic deformation of polycrystalline materials. In the “Materials
Science of Mille-feuille Structure (MFS)” project, we have been aiming at a new concept of material
strengthening by creating a layered structure with microscopic hard and soft layers, in which the easy-slip
system is significantly restricted (non von Mises condition) and hence kink deformation is effectively
induced.
Long-period stacking-ordered (LPSO)-type Mg alloys exhibit high strength only when kinkdeformation zones are introduced at high density by hot extrusion (kink strengthening phenomenon). For
example, in dilute LPSO-type Mg alloys a mille-feuille structure is formed with solute-enriched stacking
faults (SESF), which are the LPSO structural units, are randomly and sparsely arranged in the hcp-Mg
matrix, and high strength is indeed realized through kink deformation. In MFS materials science, thepossibility of kink strengthening has been investigated not only for metallic materials other than Mg alloys- steel, Ti alloys and Al alloys - but also extended to the three major materials including ceramics andpolymers. In the presentation, I will summarize the results of MFS materials science to date in terms of“elucidation of the mechanism of kink strengthening” and “extending kink strengthening to the threemajor materials”.

-18-Production and Kink Strengthening of MFS-type Mg-Zn-Y Alloy with a-Mg Single Phase
Yoshihito Kawamura
Magnesium Research Center, Kumamoto University
2-39-1, Kuro-kami, Chuo-ku, Kumamoto, 860-8555, JAPAN
Email: rivervil@kumamoto-u.ac.jp
We have succeeded in producing the MFS-type a-Mg alloys with cluster arranged nanoplates(CANaPs) in the Mg-0.4Zn-1.0Y (at%) alloy. The solute contents of this alloy are much lower - ~50%
lower in both Zn and Y - than those in other LPSO-type Mg-Zn-Y alloys [1]. The cast Mg-0.4Zn-1.0Y
alloy always has residual segregation which cannot be entirely eliminated by further heat treatment.
However, when rapidly solidified by melt spinning and subsequently consolidated by hot pressing, thesingle-phase solid solution could be obtained by a solution heat treatment. During aging, CANaPs evolvein a well-controlled manner in the a-Mg matrix of the Mg-0.4Zn-1.0Y alloy, as shown in Fig. 1. Thus, itpaves the way for a quantitative understanding of the evolution of the CANaPs and their relations withthe mechanical properties.
The four atomic layers in an fcc-type stacking sequence (ABCA) of the cluster arranged layer (CAL)
initially grow sideways until they encounter the a-Mg matrix grain boundaries. We’ve then quantitatively
studied the effect of thickness and number of the CANaPs on the strength of this MFS material. The
CANaPs thicken by growing or coalescing newer layers. The CALs in the CANaPs, unlike LPSO, areseparated by a random number of Mg layers with four or fewer atomic layers and initially grow with time.
However, at a longer aging time, the dispersion of CANaPs decreases.
The formation of kink bands during extrusion across the CANaPs was observed. The dispersion ofthese kink bands is directly related to the dispersion of the CANaPs. The yield strength is linearly related
to the dispersion of the kink band. Effectively, the presence of the CANaPs facilitates a kink bandstrengthening of the alloy. The MFS samples having dispersed CANaPs show only a limited improvementof the alloy’s tensile strength, where the tensile yield strength and the elongation were 115 MPa and 8.3 %,respectively. However, the strength improves significantly when the MFS samples were extruded at 623
K, as shown in Fig. 2. The extruded MFS-type Mg-0.4Zn-1.0Y alloy has a tensile yield strength of 368
MPa and a tensile elongation of 10.5 %. It’s comparable to the 375 MPa tensile yield strength for the
extruded LPSO-type Mg-1.0Zn-2.0Y alloy with a 26 % volume fraction of LPSO phase [1]. The MFStype Mg-0.4Zn-1.0Y alloy having half of the concentrations of both Y and Zn yields similar strength as
the LPSO-type Mg-1.0Zn-2.0Y alloy. This result clearly points out that the dispersion of CALs is more
effective in strengthening the materials than the localization of CALs in LPSO phase.

Fig. 1 HAADF-STEM micrograph of
the CANaPs composed of 1 to 3 CALs
in MFS-type Mg-0.4-1.0Y alloy.

Fig. 2 Stress-strain curves of the MFStype Mg-0.4Zn-1.0Y alloy before andafter hot-extrusion.

References[1] Y. Kawamura and S. Yoshimoto, Magnesium Technology 2005, (TMS, Warrendale, PA, 2005) 499502.

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Kink-band formation in mille-feuille structured metallic materials preparedby directional solidification
Koji Hagihara*, Toko Tokunaga
Department of Physical Science and Engineering, Nagoya Institute of Technology,
Gokiso, Showa-ku, Nagoya, Aichi 466-8555, JAPAN*Email: hagihara@nitech.ac.jp
Mg-based long-period stacking ordered (LPSO) phase with an approximate composition of
Mg12ZnY is known to contribute to increase in both of strength and ductility of Mg alloys [1]. As adeformation mode in it, kink-band formation is recently focused [2]. A kink band is a deformation band
formed by the explosive generation of dislocations in a localized region and their subsequent alignment
along a direction normal to the slip plane. Recently, the kink band was found to contribute to thestrengthening of the alloys prepared by the thermomechanical processes [3]. However, details of theformation criteria of deformation kink band have not yet been clarified. According to the study on the
LPSO phase, its unique crystal structure which is constructed by the alternative stacking of soft and hardlayers, called mille-feuille structure, are supposed as plausible factors to govern the formation of
deformation kink bands [2].
To confirm these assumptions, we have examined the deformation behavior of several directionallysolidified Mg-based and Al-based two-phase eutectic alloys with lamellar microstructure as a model
mille-feuille structured material, such as Mg/Mg17Al12 [4], Mg/Mg2Yb [5] and Al/Al2Cu [6,7].
Consequently, the formation of kink-bands was confirmed in all the mille-feuille structured alloys, as
expected (Fig. 1(b)). The details of the deformation microstructure and accompanying deformation
behavior will be discussed in the presentation.

Fig. 1 typical deformation microstructures observed in Al-16.3 at% Cu [6]References[1] Y. Kawamura et al., Mater. Trans. 42 (2001) 1172-1176.
[2] K. Hagihara et al., Intermetallics 18 (2010) 267-276.
[3] K. Hagihara et al., Acta Mater. 15 (2019) 226-239.
[4] K. Hagihara et al., Mater. Sci. Eng. A 798 (2020) 140087.
[5] K. Hagihara et al., Jour. Magne Alloys 10 (2022) 492-500.
[6] K. Hagihara et al., Mater. Sci. Eng. A 825 (2021) 141849.
[7] K. Hagihara et al., Int. Jour. Plast. 158 (2022) 103419-20-

Kink boundary formation and morphology
in wrought-processed Mg-Y-Zn alloys
Hidetoshi Somekawa1*, Yoshikazu Todaka2, Daisuke Ando3 and Motohiro Yuasa4
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan2
Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi, 441-8580, Japan
3
Tohoku University, 6-6-11 Aoba, Aramaki, Aoba-ku, Miyagi, 980-8579, Japan
4
Doshisha University, 1-3 Miyakodani, Tatara, Kyotanabe, 610-0394, Japan*
Email: SOMEKAWA.Hidetoshi@nims.go.jp
1

Kink boundary, which is introduced via wrought-processing at elevated temperatures, has taken an
attention as a new strengthening mechanism for metallic materials [1,2]. In general, as well as process
conditions such as temperature and strain rate, the processing method affects microstructure ofthermomechanical processed metallic materials, owing to the shear direction along the billet. Thissuggests that the selection of wrought-processing method leads to change the mechanical properties andmicrostructures including kink boundary; however, to the best of our knowledges, there are not any
reports about this point. In this study, we investigated the effect of wrought-processing method on themechanical property and microstructure. We also quantitatively evaluated the kink boundary fraction
through experiments, and obtained strain distribution by numerical method. Finally, the correlation
between the quantitative value and the influential factor related to strain was considered to determine thesuitable conditions for introducing kink boundaries.
Cast Mg-9at.%Y-6at.%Zn alloy was subjected by several types of wrought-processes, i.e., forging,rolling, extrusion, ECAE, caliber rolling and HPT, at the temperature of 623 K. The simple compression
test was also performed using the unique shape to consider the influential processing factors.
Microstructures of each alloy were observed by optical and laser microscopy. The fraction of kinkboundary was measured by the point-counting method [3]. The mechanical property of each wroughtprocessed and unique compressive alloys was evaluated by micro-Vickers hardness tests. As for thenumerical study, strain distributions during compressive deformation at 623 K were obtained by finite
element simulation using the DEFORM-3D software. The plastic deformation response obtained atvarious temperatures and strain rates using the same cast alloy [4] was used to this calculation.
The micro-Vickers tests shows that all of wrought-processed alloys exhibit higher hardness than thatof the cast alloy, and this value increases with the magnitude of equivalent strain, irrespective of wroughtprocessing. For instance, ECAE-ed alloys have superior hardness to that in the extruded alloys. Thisis mainly due to the difference in kink boundary formation; where an alloy with denser kink boundaries
has a possibility to exhibit higher hardness. In interesting, our previous study has pointed out, even in
fabricating at the same number of rolling passes, that the area fraction of deformation kink boundaries
and mechanical properties are influenced by the billet insert direction during caliber rolling [5]. While
the tandem- and reverse-rolled alloys have the same number of rolling passes (indicating the same
magnitude of applied equivalent plastic strain), the reverse-rolled alloy has higher hardness and a larger
kink boundary fraction as compared to those in the tandem-rolled alloy. The billets in the case of caliber
rolling are repeatably applied by “shear” with the same direction. These results propose that rather thanthe equivalent plastic strain, shear strain influences the kink band formation and mechanical property.
As comparison with kink boundary fraction measured by the point-counting method, there is somescattering of the data; whereas, shear strain has a close relationship with area fraction of kink boundaries.
References[1] Y. Kawamura, et al., Mater. Trans. 42 (2001) 1172-1176.
[2] K. Hagihara, et al., Acta Mater. 58 (2010) 6282-6293.
[3] T. Sakuma, Y. Nishizawa, Materia, 10 (1976) 279-289 (in Japanese).
[4] H. Somekawa, et al., Mater. Sci. Eng. A792 (2020) 139777.
[5] H. Somekawa, et al., Mater. Char. 175 (2021) 111080.

-21-

Self-Tuned Structure of Solute-Clusters in Dilute Mg-Zn-Y Alloy
Revealed by X-ray Fluorescence Holography
Koji Kimura1*, Daisuke Egusa2, Hidetoshi Miyazaki1, Yohei Sato3, Mitsuhiro Itakura4, Koji Hagihara1,
Naohisa Happo5, Tomohiro Matsushita6, Hiroo Tajiri7, Kouichi Hayashi1,7, and Eiji Abe2
1
Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
2
The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
3
Tohoku University, 2-1-1, Katahira, Aobaku, Sendai, Miyagi 980-8577, Japan
4
Japan Atomic Energy Agency, 178-4-4 Wakashiba, Kashiwa, Chiba 277-0871, Japan
5
Hiroshima City University, 3-4-1, Ozuka-Higashi, Asaminami-ku, Hiroshima 731-3194, Japan
6
Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan
7
Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1, Kouto, Sayo-cho, Sayo-gun,
Hyogo 679-5198, Japan*
Email: kimura.koji@nitech.ac.jp
Mg-Zn-Y alloys have received much attention as next-generation light-weight structural materials [1].
In these alloys, formation of L12-type Zn6Y8 clusters was found using transmission electron microscopy(TEM) [2], which has been discussed in relation to the superior mechanical properties. Recently,
Hagihara et al. [3] reported that such mechanical properties can be achieved even with very small
concentrations of solute-elements. However, the arrangements of these dilute solute-elements have notbeen clarified well, while aggregation of solute-elements at the stacking fault was observed by TEM [3].
X-ray fluorescence holography (XFH) can provide three-dimensional atomic configurations around a
specific element, and has been used for characterizing dopant clusters in various materials [4]. Thus,
XFH is a promising tool to determine the arrangement of dilute solute-elements in Mg matrix. In thisstudy, XFH was applied to Mg99.2Zn0.2Y0.6 alloy in order to elucidate the Zn/Y arrangements.
XFH measurements were performed at BL39XU in SPring-8, Japan. The incident X-ray energies
were set from 10.0 to 14.5 keV in steps of 0.25 keV and totally 18 Zn-Kα holograms were obtained.
Figure 1(a) shows the reconstructed atomic image around Zn. Here, the Y atomic images areobserved indicating that the Zn and Y are located almost on the same plane, although these Y images
were not present in the conventional Mg75Zn10Y15 alloy including Zn6Y8 cluster [5]. From this result, wederived a symmetry-breaking Zn3Mg3Y8 cluster as shown in Fig. 2(b) using first-principles calculations.
Here, the position of Y atoms deviates only by 0.2 Å in the c-axis direction from the Zn atoms, which issignificantly smaller than the corresponding deviation of 0.7 Å in the high-symmetric Zn6Y8 cluster. In
the talk, the electronic states of this system are also discussed, which reveals that the arrangement ofsolute-elements are self-tuned to adopt the Zn3Mg3Y8 cluster structure to enhance the phase stability
(a)

(b) 𝑐
𝑎

Zn

Zn 3 M g 3 Y 8
𝑏

Mg

Zn
Y

Zn

𝑐 axis9.4 Å

𝑎𝑏 plane

0.2Å

Y
5Å

Fig.1 (a) Atomic image around Zn in Mg99.2Zn0.2Y0.6 alloy obtained by XFH experiments. (b)Zn3Mg3Y8 cluster derived from XFH results and first-principles calculations.
References[1] Y. Kawamura et al., Mater. Trans. 42, 1172 (2001).
[2] D. Egusa and E. Abe, Acta Mater. 60, 166 (2012).
[3] K. Hagihara et al., Acta Mater. 209, 116797 (2021).
[4] K. Kimura, J. Phys. Soc. Jpn. 91, 091005 (2022).
[5] T. Nishioka et al., Materialia 3, 256 (2018).

-22-

Direct observation of pseudo-gap electronic structure in the Mg-Zn-Y alloys studied byhard X-ray photoelectron spectroscopy
Hidetoshi Miyazaki1*, Tatsuyoshi Akatsuka1, Koji Kimura1, Daisuke Egusa2, Yohei Sato3, Mituhiro
Itakura4, Toko Tokunaga1, Kouichi Hayashi1, Koji Hagihara1, and Eiji Abe2
1
Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, JAPAN2
The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
3
Tohoku University, 2-1-1, Katahira, Aobaku, Sendai, Miyagi 980-8577, Japan
4
Japan Atomic Energy Agency, 178-4-4 Wakashiba, Kashiwa, Chiba 277-0871, Japan*Email: miyazaki@nitech.ac.jp
Mg alloys doped with transition metal and rare earth element having a long-period stacking structure
are attracting attention as next-generation lightweight structural materials due to their excellent properties
of ultra-high strength, flame retardance, and light weight. The excellent functionality and stability are
believed to be due to the dispersion of the added elements in the Mg matrix to form local clusters. In the
Mg99.2Zn0.2Y0.6 alloy [1], it has been experimentally determined by X-ray fluorescence holography method
by K. Kimura that local cluster structures different from those in previous Mg-Zn-Y alloys are formed.
However, it is still unclear how the existence of these local clusters contributes to the stabilization of theelectronic structure in Mg-Zn-Y alloys. In this study, we have investigated the electronic structure of
Mg99.2Zn0.2Y0.6 alloy by hard X-ray photoelectron spectroscopy (HAXPES), which can directly observe
the electronic structure near the Fermi level that contributes to phase stabilization, to gain insight into themechanism of phase stabilization in Mg-Zn-Y alloy systems.
Mg99.2Zn0.2Y0.6 single-crystal sample was prepared by the Bridgman method [1]. Mg was also measured
as a reference sample. HAXPES measurements were performed at the BL09XU beamline of SPring-8.
All photoemission spectra were recorded at 30 K. Clean surfaces of the materials for HAXPES
measurement was obtained by ex-situ scraping with a diamond file and immediately installing the samples
in the HAXPES chamber. Fermi level and total energy resolution were determined by the Fermi edge of
evaporated gold films. The total energy resolution of the HAX-PES measurement was set to 180 meV atthe excitation photon energies of 7942 eV.
Figure 1 shows the valence band
photoemission spectra of Mg99.2Zn0.2Y0.6 and Mg
near the Fermi level. A peak associated with
Fermi surface Brillouin zone interaction around
0.3 eV was observed in both Mg99.2Zn0.2Y0.6 andMg alloys, and a pseudogap-like electronic
structure was observed near the Fermi level. The
pseudogap structure near the Fermi level isshifted to the higher binding energy side in the
Mg99.2Zn0.2Y0.6 alloy compared to Mg alloy,
suggesting that the pseudogap is deeper than in
Mg alloy. This result suggests that the energy
gain of the electronic system in Mg-Zn-Y alloys
Fig. 1 Valence band photoemission
contributes to the phase stability in this alloy.
In the presentation, the phase stability of Mgspectra of Mg99.2Zn0.2Y0.6 and Mg alloys with
Zn-Y alloys will be discussed in detail together hν = 7942 eV. Inset shows the photoelectronwith the results of first-principles calculations.
spectra of metallic gold film.
References[1] K. Hagihara et al., Acta Mater. 209, 116797 (2021).

-23-

Temperature and strain dependence of plastic deformation behavior of long-period
stacking-ordered magnesium alloys
Tomotaka Miyazawa1*, Ryo Endo1, and Toshiyuki Fujii1
Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8552, JAPAN*Email: miyazawa.t.ab@m.titech.ac.jp

1

Plastic deformation behavior in long-period stacking ordered (LPSO) magnesium alloys, including theformation of a kink-band, has been investigated by many researchers recently. Hagihara et al. reported
the temperature dependence of the strain rate sensitivity factors of directional solidified (DS) Mg−Zn−Y
alloys with 14H, 18R, and 10H LPSO structures [1]. In the temperature range of 293–573 K, the strain
rate sensitivity (m) factors were negative, and the Portevin−Le Chatelier (PLC) effect was observed in all
the alloys. These results indicated that the dynamic segregation of Y and Zn occurred at the boundariesof the kink-bands and impedes their migration. Conversely, low temperatures (< 250 K) hider the
diffusion of solute atoms, causing the PLC effect to disappear and the strain rate sensitivity to change
from negative to positive. However, there have been no studies on the m values at temperatures below
room temperature. Therefore, in this study, to discuss the plastic deformation behavior of the LPSO Mg
alloys, the investigation of the strain rate sensitivity m was conducted with strain rate jump tests at low
temperatures.
The DS Mg−6at%Zn−9at%Y alloy composed of the 18R LPSO phase was used. The rectangularcompression test specimens were cut to the required dimensions (2 mm × 2 mm × 5 mm) by an electricaldischarge machine. The compression axis is parallel to the growth direction. The strain rate jump tests
were carried out between the strain rates of 1.67 ×
10−4 s−1 and 1.67 × 10−3 s−1 at temperatures ranging
from 89 to 296 K under the atmospheric pressure.
The m value was calculated from the change in theflow stress with the jump in strain rate.
Fig. 1 shows true stress−true plastic strain curves
at each temperature. The flow stress curve exhibited
serration, with a drop occurring after yielding causedby the formation of kink-bands. In the middle andlater stages, linear work hardening was observed at
all temperatures. Fig. 2 shows the strain dependenceof the m value. The m values decreased withincreasing the true plastic strain in this alloy. At 296
K, although the m values were positive in the earlyFig. 1 True stress−true plastic strain curves.
stage of the plastic deformation, they became
negative and the PLC effect appeared as true plasticstrain exceeded 10%. In contrast, at 89 K, the mvalues remained positive and the PLC effectdisappeared. The temperature and strain dependenceof the m value observed in this study are the same as
for a Au-Cu alloy [2]. That means the plastic
deformation behavior of the 18R LPSO Mg alloy
including the kink-band formation, is similar to thatof a solid solution alloy.
References[1] K. Hagihara et al., Mater. Lett., 214 (2018)
119−122.
[2] S. H. van den Brink et al., Phys. Stat. Sol. (a),30 (1975) 469−477.

-24-

Fig. 2 True plastic strain-dependence of m value.

Microstructure and hardness in Mg-Y-Zn alloys with long-periodic stacking ordered phaseprocessed by equal-channel-angular extrusion
Motohiro Yuasa1*, Ryoichi Sato1, Daisuke Ando2, Yoshikazu Todaka3, Hiroyuki Miyamoto1 and Hidetoshi
Somekawa4
1
Doshisha University, 1-3 Miyakodani, Tatara, Kyotanabe, 610-0394, Japan
2
Tohoku University, 6-6-11 Aoba, Aramaki, Aoba-ku, Miyagi, 980-8579, Japan3
Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi, 441-8580, Japan
4
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan**
Email:myuasa@mail.doshisha.ac.jp
Recently, magnesium alloys containing the long-period stacking order (LPSO) phase have been attracting
attention because of their strength exceeding the high-strength aluminum alloys [1]. It has been reported that
this high strength is due to the formation of deformation kink bands by wrought-processing methods [2]. Our
previous study has reported the effects of wrought-processing methods on the formation of the kink bands andtheir mechanical properties [3]. The study has suggested that the strain introduced into the specimens by thewrought-processing methods affects the formation of kink bands and mechanical properties. In this study, we
focused on the equal-channel-angular extrusion (ECAE) process, in which strong shear is applied to specimens.
The objective of this study was to evaluate the effect of the strong shear during the ECAE process on theformation of kink bands and their mechanical properties.
The cast Mg-9at%Y-6at%Zn alloys were processed by
ECAE at 623 K with a ram speed of 1 mm/min. The ECAE wascarried out up to three passes using route Bc. The microstructure
was observed using a laser microscope, and the area fraction of
deformation kink bands was measured by the point-counting
method. The hardness of the specimens was measured by microVickers hardness tests under the indentation load of 300 gf and
10 gf. Using local hardness with the indentation load of 10 gf,
the magnitude of kink bands strengthening was estimated bysubtracting the hardness in the area where kink bands wereobserved with the laser microscopy from that in the area wherekink bands were not observed [4].
Figure 1 shows the microstructure of ECAEed specimens.
The area fraction of the deformation kink bands tended toincrease with the number of ECAE passes. The result of microVickers hardness tests shows that the hardness increased withthe area fraction of the kink bands. However, the magnitude ofincrease in local hardness related to kink band strengthening wascomparable to the forged alloys [4] despite the strong shear
deformation induced by ECAE. This suggests that the shear
strain induced by ECAE is effective for increasing the area
fraction of kink bands in the entire specimens, but not effective
for a higher density of kink boundaries in the local region.
Fig. 1. Deformation microstructure in
the ECAEed alloys: (a)1pass and (b)3pass. The black arrows indicate theReferences
kink bands.
[1] Y. Kawamura et al., Mater. Trans. 42 (2001) 1172-1176.
[2] K. Hagihara et al., Acta Mater. 163 (2019) 226-239[3] H. Somekawa et al., Mater. Lett. 304 (2021)130653.
[4] Y. Nakasuji et al., Mater. Lett. 292 (2021) 129625.

-25-

Ripplocations: A Universal Deformation Mechanism in Millefeuile Solids
Michel W. Barsoum
Department of Materials Science and Engineering
Drexel University, Philadelphia, PA, USA*
Email: barsoumw@drexel.edu

Geologic formations and layered materials/solids - such as laminated composites, card decks,
wood, the MAX phases, mica, graphite, etc. will, when compressively loaded edge-on, fail bybuckling, that can result in kink bands. Recently we have shown that ripplocations and notbasal dislocations, BD, are responsible for kink band formation. Ripplocations, at least ingraphite, are highly mobile, fully reversible, dissipative waves that form as a result of confinedbuckling. When standing, the crests and troughs of the waves define ripplocation boundaries– also by definition fully reversible - that, beyond a critical load, naturally transform into
ripplocation boundaries, that share some similarities to kink boundaries are fundamentallydifferent. By confining and indenting decks of cards, thin steel or Al sheets edge-on with acylindrical indenter we nucleated and propagated ripplocations. Molecular dynamics, MD,
simulations in graphite at 10 K and Ti3AlC2 nucleated and propagated ripplocations that, but
for scale, were identical to those nucleated in our macroscopic experiments. In this talk, a firstattempt to model the mechanics of ripplocation nucleation and propagation is presented. We
also show that the observed energies dissipated per cycle can be accounted for by Coulombic
friction between the layers. As importantly direct compelling evidence for ripplocations in highresolution TEM images of the MAX phases, graphite and mica are presented. The latter being
quite similar to those modelled by MD. Lastly, we predict the presence of a new type of basal
dislocations pairs in the MAX phases whose core energies and mobilities are relatively low [2].
The implications of these discoveries for our understanding of the deformation of layered solids
is profound and will be touched upon.

Fig. 1. Molecular dynamics of ripplocations in Ti3AlC2. [1]References[1] Plummer, G.; Rathod, H.; Srivastava, A.; Radovic, M.; Ouisse, T.; Yildizhan, M.; Persson, P. O. Å.; Lambrinou, K.;
Barsoum, M. W.; Tucker, G. J., On the Origin of Kinking in Layered Crystalline Solids. Mat. Today, 43, 2021, 45-52.
[2] Plummer, G.; Tucker, G. J.; Barsoum, M. W.; Weinberger, C. R., Basal Dislocations in MAX Phases: Core Structureand Mobility. Materialia 2021, 10130.

-26-Effects of Kink Boundaries on High Temperature Deformation Behavior of
Textured Ti3SiC2 MAX Phase Sintered Body
Ken-ichi Ikeda1*, Nana Hashimoto1, Yuji Shirakami1, Seiji Miura1,
Koji Morita2, Tohru S. Suzuki2, and Yoshio Sakka2
1
Hokkaido University, Kita13, Nishi8, Kita-ku, Sapporo, Hokkaido, 060-8628, JAPAN
2
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, JAPAN*Email: ikeda.ken-ichi@eng.hokudai.ac.jp
The ternary MAX phase ceramics have the general formula Mn+1AXn, where “M” is an early transition
metal; “A” is group A element; “X” is C and / or N, and n = 1, 2, 3. The MAX phase ceramics areclassified as mille-feuille materials because of their hard-soft two-layered structure consisting of MX andA layers due to the difference in bonding strength. It is also known to be a novel material that combines
ceramic and metallic properties due to the difference in its bonding strength. Focusing on plastic
deformation, it has been reported that kink deformation occurs in many MAX phase ceramics during
deformation and fracture [1]. We have successfully fabricated textured dense and porous Ti3SiC2, a kind of
MAX phase ceramics, sintered bodies, and investigated various mechanical properties and deformation
structures [2-4]. The objective of this study is to clarify the effect of kink boundaries on high temperature
deformation behavior using these textured sintered bodies.
In this study, commercial Ti3SiC2 powder was used. Textured dense and porous Ti3SiC2 sinteredbodies were prepared by slip casting in a strong magnetic field (12T) followed by spark plasma
sintering (SPS). Specimens of textured dense sintered body with the compression axis perpendicular tothe c-axis direction were prepared, and kinks were introduced by compressive deformation at 1200°C
up to 6.8% using SPS machine. Compression specimens were prepared from textured dense with kink,textured dense, and textured porous sintered bodies. The direction of the compressive axis was 45° tothe c-axis direction. High temperature compression tests were conducted at 1200°C in vacuum and at astrain rate of 3×10-4 s-1. SEM-BSE observation, EBSD analysis, and TEM/STEM observation werecarried out to observe the microstructures of the specimens before and after the compression tests.
Compression tests at 1200°C showed plastic deformation in all cases, and the 0.2% proof stress was
the highest for the oriented dense sintered specimens. It was suggested that the pores introduced inadvance and the delamination induced during the kink deformation process affected the 0.2% proof stress.
On the other hand, a comparison of the work hardening exponent n values showed that the kinked
specimens tended to be larger than the other specimens. Microstructural observations also revealed aunique structure in the deformed microstructure in the vicinity of the introduced kink boundary. Fromthese results, it is considered that the introduction of kink in MAX phase ceramics causes a kinkstrengthening that affects the work-hardening behavior.
Acknowledgments
This work was supported by JSPS KAKENHI (Grant Numbers JP19H05115, JP21H00087, andJP18H05482).
References[1] M. W. Barsoum and M. Radovic: Annu. Rev. Mater. Res., 41 (2011), 195-227.
[2] Y. Shirakami, K. Ikeda, S. Miura, K. Morita, T. S. Suzuki and Y. Sakka: J. Jpn. Soc. Powder Powder
Metallurgy, 67 (2020), 607-614.
[3] N. Hashimoto, K. Ikeda, S. Miura, K. Morita, T. S. Suzuki and Y. Sakka: J. Japan. Inst. Met. Mater., 85(2021), 256-263.
[4] N. Hashimoto, K. Ikeda, S. Miura, K. Morita, T. S. Suzuki and Y. Sakka: Mater. Trans., 63 (2022),
133-140.

-27-

Atomistic analysis of microscopic mechanisms of kink formation
in metallic and ceramic mille-feuille structures
Hajime Kimizuka1* and Rana Hossain2
Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603, JAPAN
2
Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka, 560-8531, JAPAN*Email: kimizuka@me.es.osaka-u.ac.jp
1

The reinforcing phase of Mg alloys with a mille-feuille (MF) structure or LPSO structure ischaracterized by a layered structure, in which hard layers enriched with solute elements and soft layers
composed of Mg are arranged on the nanometer order. A kink formation accompanied by crystal rotation
during deformation results in high strength. Kink bands induced by stress loading have been observed ina wide range of materials, not limited to Mg-based MF structures. To elucidate the mechanisms of changes
in mechanical properties and strengthening due to the introduction of kinks, it is useful to understand thesimilarities and differences between various MF structures in which kinks are frequently observed. In thisstudy, we investigated the microscopic mechanisms of kink formation in different types of MF structuresand clarified their characteristics by capturing the microscopic elementary processes during plastic
deformation of metallic and ceramic MF structures using atomic-level simulation methods.
A Cu-Nb nanolamellar structure was taken as an example of a mettalic MF structure to investigate themicroscopic elementary processes during plastic deformation. Molecular dynamics simulations were
performed to analyze the behavior of dislocations emitted from the lamellar interfaces, as well as theatomic-level microstructures observed in the deformation process of the lamella structure. The results
showed that the interface acts as both a source and sink of dislocations during compressive deformation
parallel to the lamellar interface, and that large plastic deformation occurs without interlayer delamination.
Furthermore, it was confirmed that a sharp kink is formed due to elastic buckling when the layer thickness
is small, while a blunt kink is gradually formed by a combination of complex plastic deformation
processes as the layer thickness increases.
A Ti3(Si,Al)C2 MAX phase was taken as an example of a ceramic MF structure. The Ti3(Si,Al)C2
crystal consists of hard Ti6C octahedral layers and soft (Si,Al) layers alternately stacked in the c-axis
direction, and the difference in slip between the two layers causes significant anisotropy in deformation.
When compressed at 45° to the basal plane, slip deformation was dominant due to the activity of
dislocations in the basal planes, whereas when compressed at an orientation close to parallel to the basal
plane, kink formation was observed due to the cooperation of dislocation activity and interlayer
delamination along the basal planes. In addition, the generation and activity of ripplocations played an
important role in this process. The basal dislocation, which is a component of the kink interface, showedsignificant asymmetry in mobility depending on the dislocation component and the position of the slip
plane [1, 2].
References[1] R. Hossain, H. Kimizuka, Y. Shiihara, S. Ogata, Comput. Mater. Sci. 209 (2022) 111366.
[2] R. Hossain, H. Kimizuka, S. Ogata, under review (2022).

-28-

Kink Strengthening in TiNi-Nb and TiCo-Nb Alloys with Eutectic Mille-feuille Structure
Kazuhiro Ishikawa1*, Kanta Ohno1 and Yoji Miyajima1
Kanazawa University, Kakuma, Kanazawa, Ishikawa, 920-1192, JAPAN*Email: ishikazu@se.kanazawa-u.ac.jp
The TiNi-Nb and TiCo-Nb alloys are strong candidates for next-generation hydrogen separation andpurification materials to replace Pd-based alloys. Since Nb shows severe hydrogen embrittlement, TiNi
or TiCo phase is added to Nb to achieve both hydrogen permeability and resistance to hydrogen
embrittlement. The TiNi (TiCo)-Nb alloy has an eutectic Mille-feuille structure consisting of B2-TiNi(TiCo) and bcc-Nb phases [1, 2]. Since hydrogen flux passing through the alloy is inversely proportion
to the alloy thickness, thin alloy membrane is produced by rolling industrially. Thus, its mechanicalproperties are also important. In this research, kink formation, thermal stability of microstructure andmechanical properties of TiNi (TiCo)-Nb alloys were investigated, and kink strengthening effects inthese alloys are estimated quantitatively on the basis of the experimental data.
The TiNi (TiCo)-Nb alloys were prepared by arc melting. The samples, cut from the ingots using anelectrical discharge machine, were rolled at room temperature, and annealed at different temperatures inan electric furnace. Microstructural observations were carried out using scanning electron microscopy(SEM). The Vickers hardness of the samples were measured by a micro-Vickers testing machine.
Tensile tests were carried out using a tensile testing machine with an initial strain speed of 0.83 s-1.
SEM micrographs of (a) as-cast and (b) 30% rolled TiNi-Nb (Ti40Ni41Nb19) alloys are shown in Figs.
1. The eutectic type mille-feuille structure consisting TiNi (gray) and Nb (white) phases was clearlyobserved in the (a) as-cast alloy. After rolling, layer bending occurred without peeling of TiNi/Nb phase,as shown in Fig. 1(b). The Vickers hardness increased from 321 for the as-cast alloy to 366 for rolled
one, which indicates that the TiNi-Nb alloy was strengthened by introduction both dislocations andkinks. After annealing at 923 K for 1 h, the hardness recovered to the same value for the as-cast alloy.
Furthermore, kinks remained in this sample after annealing. Therefore, an alloy having a mille-feuillestructure including kinks but no dislocations can be obtained. The yield stresses of as-cast, 30% rolled
and annealed (at 923 K) alloys were obtained as 529, 783 and 577 MPa by tensile tests, respectively.
Here, yield stress of rolled alloy can be expressed by the following equation:
σrolled= σas-cast+ Δσd + Δσk(1)yy
as-castwhere σyis the yield stress of the as-cast alloy, and strengthening effects by dislocations and kinks
are defined as Δσd and Δσk , respectively. Comparing the yield stresses of as-cast, rolled and annealed
alloys, the extent of the strengthening effects of dislocations and kinks can be estimated to be about 210
and 50 MPa, respectively. In the case of TiCo-Nb alloys, larger kink strengthening and smaller
dislocation strengthening effects were estimated than those of TiNi-Nb alloys. In conclusion, we candemonstrate that the TiNi (TiCo)-Nb alloys having a mille-feuille structure consisting B2 and bcc
phases are strengthening by kinks.

Figs. 1 SEM micrographs of (a) as-cast and (b) rolled TiNi-Nb (Ti40Ni41Nb19) alloys.
References[1] K. Hashi et al., J. Alloys Compd. 368 (2004) 215-220.
[2] K. Hashi et al., J. Alloys Compd. 425 (2006) 284-290.

-29-

Plasticity enhanced in kinking orientations of cubic-structured ceramics micropillars
Hiroshi Masuda1*, Yelm Okuyama2, and Hidehiro Yoshida1, 3
Department of Materials Science and Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku,
Tokyo, 113-8656, Japan
2
National Institute of Technology, Kisarazu College, 2-11-1 Kiyomidai-Higashi, Kisarazu, Chiba 2920041 Japan3
Next Generation Zirconia Social Cooperation Program, The University of Tokyo, 2-11-16, Yayoi,
Bunkyo-ku, Tokyo 113-8656, Japan*
Email: masuda@material.t.u-tokyo.ac.jp

1

Ceramics materials exhibit superior mechanical strength but with low ductility and toughness. As apotential strategy to overcome the brittleness, we have focused on the feasibility of kink toughening in
ceramics, where kink formation contributes to small-scale plasticity and enhances ductility and/or
toughness. Our recent studies found that kink formation is associated with enhanced energy absorption
densities during compressions in near-[111] orientations of Y2O3-stabilized ZrO2 (YSZ) ceramics [1, 2].
In this study, orientation-dependent plasticity of several cubic-structured oxide ceramics, such as 10
mol% Y2O3-stabilized ZrO2 (10YSZ; fluorite), non-doped Y2O3 (bixbyite) and non-doped SrTiO3(perovskite) was investigated through single-crystal micropillar compression experiments from various
orientations. Cylindrical micropillars with diameters of 0.9–1.1 μm and heights of 2.5–4.0 μm were
fabricated via a focused ion beam technique and compressed at room temperature with an initial strain
rate of 1 × 10−3 s−1 using a nanoindentation facility equipped with a flat-ended diamond tip. Surface slip
trace analysis and cross-sectional dislocation characterization were performed by scanning electron
microscopy (SEM) and transmission electron microscopy (TEM), respectively. Furthermore, orientation
dependence of strain and dislocation structure developments inside 10YSZ micropillars were numericallysimulated using a crystal plasticity finite element method (CPFEM).
Nominal stress–strain curves of 10YSZ micropillars compressed at room temperature along different
orientations are demonstrated in Fig. 1, indicating a significant orientation dependence in the plastic
deformability. The [001] and [101] compressions exhibit
plastic yielding but were associated with earlier fracture
at strains below 10%. In contrast, extensive deformability
is recognized in the compression along the [111] direction(i.e., the kinking orientation), where the pillar exhibitedno fracture up to the nearly 40% strain. This enhanced
plasticity could be associated with dislocation activities
on multiple {001}<110> slip systems, as revealed by theslip trace analysis and dislocation characterization
through SEM and TEM observations. Such plastic
anisotropies were also observed in Y2O3 and SrTiO3
micropillars, where considerable plasticity was achieved
with multiple slip activations.
The CPFEM simulation demonstrated that the
deformation homogeneity was enhanced with increase insecondary slip activities. This suggests that the enhanced
deformability at kinking orientations of 10YSZ (andFig. 1 Nominal stress–strain curves ofpossibly other cubic-structured ceramics) is attributed to
10YSZ micropillars compressed at room
the enhanced deformation homogeneity and suppression oftemperature along different orientations.
slip localization as the trigger of brittle fracture.
Acknowledgement: This study was supported by JSPS KAKENHI for Scientific Research on Innovative
Areas “MFS Materials” (21H00091).
References: [1] H. Masuda, K. Morita, M. Watanabe, T. Hara, H. Yoshida, and T. Ohmura, Acta Mater.,
203 (2021) 116471. [2] H. Masuda, Materia Japan, 60 (2021) 96–100.

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Nanoindentation Examination of Kink Boundary Hardness in Ti3SiC2 MAX Phase
Koji Morita1,2,3*, Daiki Matsui1,2, Daisuke Terada2, Ken-ichi Ikeda3, Seiji Miura3 and Takahito Ohmura1,3
1
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, JAPAN
2
Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, 275-0016, JAPAN
3
Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 891-0395, JAPAN4
Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo 060-8628, JAPAN*Email: MORITA.Koji@nims.go.jp
The MAX phase ceramics, which can be expressed by the formula of Mn+1AXn (n = 1∼3), haveattracted much attention as multi-functional materials because those can simultaneously possess ceramicand metallic-like properties due to its unique bonding nature [1-3]. Since the MAX phase ceramics withhexagonal structure have frequently reported kink formation through deformation, it is expected to exhibit
king strengthening similar to that of LPSO-type Mg alloys [4,5]. This study, therefore, was carried out toexamine the possibility of kink strengthening in the MAX phases using the Ti3SiC2 polycrystal as areference material, which is known as the most representative MAX phases. In order to examine the kinkstrengthening in the Ti3SiC2-MAX phase, kink boundaries were formed by high temperature compressive
tests, and then, nanoindentation tests were performed around the kink boundaries with several charactersformed through the compressive creep test [6].
First, polycrystalline Ti3SiC2 MAX phase was prepared by a reaction sintering process using a
spark-plasma-sintering (SPS) technique. In order to examine mechanical properties, nanoindentation tests
were conducted around the formed kink bands. The kink boundary showed that the nanohardness linearlychanged with the distance from the kink bands and showed higher values around the kink bands. Since
the kink bands blocked the slip line caused by the nanoindentation, those become obstacles against thedislocation motion caused by the indentation deformation. This suggests that the kink bands would
contribute to improving the mechanical properties of the Ti3SiC2 MAX phase.
References[1] M.W. Barsoum, M. Radovic, Annu. Rev. Mater. Res., 41 (2011) 195–227.
[2] Z. M. Sun, Int. Mater. Rev., 56 (2011) 143–166.
[3] Z. Huang, H. Xu, H. Zhai, Y. Wang, Y. Zhou, Ceram. Int., 41 (2015) 3701–3709.
[4] M. Yamasaki, K. Hashimoto, K. Hagihara, Y. Kawamura, Acta Mater., 59 (2011) 3646–3658.
[5] K. Hagihara, Z. Li, M. Yamasaki, Y. Kawamura, T. Nakano, Acta Mater., 163 (2019) 226–239.
[6] D. Matsui, K. Morita, D. Terada, K. Ikeda, S. Miura, Mater. Trans. 63[7] (2022) 1055-1064.

-31-

Microstructure, Deformation and Property of Wrought Magnesium Alloys
Jian-Feng Nie1*, Kwang-Seon Shin2, and Zhuoran Zeng3
Monash University, Clayton, Melbourne, Victoria 3800, AUSTRALIA
2
Seoul National University, 1 Gwannak-ro, Gwannak-gu, Seoul 08826, REPUBLIC OF KOREA
3
The Australian University, Canberra, ACT 2601, AUSTTRALIA*Email: jianfeng.nie@monash.edu
1

Pure magnesium develops a strong basal texture after conventional processing of hot rolling or
extrusion. Consequently, it exhibits anisotropic mechanical properties and is difficult to form at room
temperature. Adding appropriate alloying elements can weaken the basal texture or even change it, but
the improvement in formability and mechanical properties is still far from expectations. Over the past
20 years, considerable efforts have been made and significant progress has been made on wrought Mg
alloys at the fundamental and technological levels. At the fundamental level, textures formed in sheetsand extrusions of different alloy compositions and produced under different strain paths orthermomechanical processing conditions are relatively well established, with the assistance of theadvanced characterization technique of electron backscatter diffraction. At the technological level, room
temperature formability of sheet has been significantly improved, and tension-compression yieldasymmetry of extrusion is also remarkably reduced or eliminated. This talk starts with a review of
microstructure (texture and grain size) and deformation of polycrystalline pure Mg with different
textures, grain sizes, and loading conditions. With this information as a base, texture, grain size anddeformation of polycrystalline Mg-alloy sheets and extrusions produced under different processing
conditions, are examined and compared. Remaining and emerging scientific and technology issues arethen highlighted and discussed in the context of texture and grain size. The need for better-resolution
diffraction and spectroscopy techniques will also be discussed in the relationship between texturechange and grain boundary solute segregation.
Reference[1] J.F. Nie, K.S. Shin and Z.R. Zeng, Metall. Mater. Trans. A 51A (2020) 6045-104.

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Tensile and compressive mechanical behaviour in fully-lamellar extruded
MgGd2Zn1 alloy.
G.Garcesa,*, P. Pereza, J. Medinaa, R. Bareab, H. K. Limc, S. Kimc, E. Maawadd, N.
Shelld, P. AdevaaaDepartment of Physical Metallurgy, CENIM-CSIC, Avenida Gregorio del Amo 8, E28040 Madrid, Spainb
Departamento de Ingeniería Industrial, Universidad Nebrija, Campus Dehesa de laVilla, C. Pirineos 55, 28040 Madrid, Spainc
Casting Research, Korea Institute of Industrial Technology (KITECH) 7-47 Songdodong, Yeonsu-gu, Incheon 406-840, Korea
dInstitute of Materials Physics, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1,
21502 Geesthacht, Germany
Abstract
The tension and compression behaviour in the extruded ECO-MgGd2Zn1 (%at.) alloy
with fully lamellar structure has been evaluated following the evolution of the internalstrains during in-situ tension and compression tests. Before extrusion, a thermal treatment
is carried out in the alloy to promote the formation a lamellar structure within magnesium
grains. After extrusion at 350 ºC, the microstructure is characterised by a 14H-LPSO
fibres elongated along extrusion direction, dynamic recrystallised grains of around 1 m
and coarse highly-oriented non-dynamic recrystallised grains. The 14H-LPSO fibers
behave as a reinforcement. After yielding, internal strains of grain orientations favourable
oriented for yielding exhibits a strong relaxation. Under compression, the activation oftwinning is observed but lamellae within grain delay twinning propagations. The
activation of <a> dislocation slip along the basal plane controls the beginning of theplastic deformation.

Figure 1. a) Microstructure of the ECO-MgGd2Zn1 (%at.) alloy after lamellae-formation
thermal treatment and a) extruded at 350 ºC.

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Hot deformation of Mg-Y-Zn alloy with different content of the LPSO phase studied byin-situ synchrotron radiation diffraction
Klaudia Fekete1, Daria Drozdenko1, Patrik Dobroň1, Gergely Farkas2, Domonkos Tolnai3, Jan Čapek4
and Kristián Máthis 1*
1

Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University, Ke
Karlovu 5, 121 16 Prague, Czech Republic
2
Nuclear Physics Institute of the CAS, Hlavní 130, 250 68, Řež, Czech Republic
3
Institute of Materials Science, Helmholtz-Zentrum Geesthacht, Max-Planck Str. 1, Geesthacht,
D21502, Germany
4
Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, Villigen PSI, 5232,
Switzerland*
Email: mathis@met.mff.cuni.cz

The compressive deformation behavior of the extruded Mg-Y-Zn magnesium alloys containing a low(~10%) and high (~85%) amount of long-period stacking ordered (LPSO) phase was studied by in-situ
synchrotron radiation diffraction technique [1,2]. Tests were conducted at temperatures between room
temperature and 350 °C. Detailed microstructure investigation was provided by scanning electron
microscopy, particularly the backscattered electron imaging and electron backscatter diffraction
technique. The as-extruded microstructures exhibit a recrystallized α-Mg phase with nearly random
texture. The LPSO phase, identified as the 18R polytype, is represented by wavy lamellae elongated along
the extrusion direction and has an intensive basal texture.
For the low LPSO content alloy, the results show that twinning lost its dominance and kinking of the
LPSO phase became more pronounced with increasing deformation temperature. Neither cracks of the
LPSO phase nor debonding at the interface between the LPSO phase and the Mg matrix were observed attemperatures above 200 °C. At 350 °C, the LPSO phase lost its strengthening effect and the dynamic
recrystallization of the Mg matrix is dominant [1]. The alloy with high volume fraction of the LPSO phaseexhibit a superior yield strength of 480 MPa, if it is compressed along the extrusion direction at room
temperature [2]. With increasing deformation temperature, the yield strength is reduced by 15% at 200°C and by 46% at 300 °C, respectively. At all tested temperatures, the basal slip is activated in the α-Mgmatrix far below the yield strength. The macroscopic yielding of the alloy is controlled by the activationof deformation kinking in the LPSO phase. The synchrotron radiation diffraction data indicate the stresslocalization at kinks.
References[1] K. Horváth Fekete, D. Drozdenko, J. Čapek, K. Máthis, D. Tolnai, A. Stark, G. Garcés, P. Dobroň,Journal of Magnesium and Alloys, 8 (2020) 199-209.
[2] K. Fekete, G. Farkas, D. Drozdenko, D. Tolnai, A. Stark, P. Dobroň, G. Garcés, K. Máthis,Intermetallics, 138 (2021) 107321.

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Monitoring of strengthening of LPSO in αMg/LPSO dual phase alloy by hot-extrusion
using in situ neutron diffraction during deformation
Stefanus Harjo1*, Kazuya Aizawa1, Wu Gong1, Takuro Kawasaki1, and Michiaki Yamasaki2
1
J-PARC Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki, 119-1195, JAPAN
2
Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, JAPAN*Email: stefanus.harjo@j-parc.jp
The strength of Mg-Zn-Y alloys containing LPSO was found to be enhanced by post mechanicalprocesses such as hot-extrusion [1] or hot-rolling [2]. The increase in strength is considered due to theintroduction of kink-bands in LPSO by the post mechanical processes.[1] The yield stress of Mg89Zn4Y7
containing 86-vol% LPSO increased monotonically by hot-extrusion and with increasing the extrusion
ratio (R), which was explained by the increased amount of kink bands and the texture development in
LPSO [3]. The yield stress of Mg97Zn1Y2 containing 25-vol% LPSO increased by hot-extrusion with thesmall R value, but it decreased as the R value increased due to the occurrence of dynamic recrystallization
in αMg during hot-extrusion with the high R value.[4] These reports show that the effects of hot-extrusion
to the microstructures and strengthening of αMg and LPSO were different, and the understanding ofstrengthening mechanism that was evaluated mainly from the macroscopic yielding behavior may be notenough without knowing the individual phase stresses.
Thus, in this study, in situ neutron diffraction during deformation was performed using three kinds ofsamples of Mg97Zn1Y2 alloy: an as-casted sample (As-Cast), hot extruded samples with the R values of
5.0 (R=5.0) and 12.5 (R=12.5). The reason for varying the R value is to extend the kink amount in LPSO
and change the microstructure of αMg in the starting materials before deformation. Fig. 1 shows thegeometrical illustration of experimental setup for in situ neutron diffraction experiment during
deformation and the tensile true stress-true strain curves of the three samples. Crystallographic evolutionsof αMg and LPSO by hot-extrusion and deformation behavior of the individual phases were investigated,
and the unique deformation mechanism by hot-extrusion in this alloy will be discussed based on theobtained results.
Applied true stress (MPa)

Neutron

Slit

Radialcollimator

Tensileloading

400

R = 12.5300

200

As-Cast

100

0
0.00

Specimen

R = 5.0

0.04

0.08

0.12

0.16

0.20

Applied true strain

Fig. 1. Geometrical illustration of experimental setup for in situ neutron diffraction experiment during
deformation and tensile true stress-true strain curves of the three samples..
References[1] M. Yamasaki, T. Anan, S. Yoshimoto, Y. Kawamura, Scr. Mater. 53 (2005) 799–803.
[2] T. Itoi et al., Mater. Sci. Eng. A 560 (2013) 216–223.
[3] K. Hagihara, Z. Li, M. Yamasaki, Y. Kawamura, T. Nakano, Acta Mater. 163 (2019) 226–239.
[4] M. Hirano et al., Mater. Trans. 51 (2010) 1640–1647.

-35-

Kink strengthening of LPSO Mg-Zn-Y alloys after processing by high-pressure sliding(HPS)
1

Yongpeng Tang1*, Shinichi Inoue2, Yoshihito Kawamura2 and Zenji Horita1, 2, 3
Kyushu Institute of Technology, 1-1 Sensuicho Tobata-Ku, Kitakyushu, 804-8550, JAPAN
2
Kumamoto University, 2-39-1 Kurokami Chuo-ku, Kumamoto, 860-8555, JAPAN3
Saga University, 1 Honjo-machi, Saga, 840-8502, JAPAN,*Email: tayopeng@gmail.com

Formation of kink bands, which are induced in the long-periodic stacking ordered (LPSO) phase,
have been attracted attention, because these kink bands play a role in preventing dislocation motion andresult in enhancing the strength [1,2]. It was shown that kink bands formed in the LPSO phase during
hot extrusion processing [3,4] and several other processings such as hot compression, high-pressure
torsion (HPT) and caliber rolling [5,6]. However, it is an issue how to induce a high density of kinkbands in the LPSO phase.
High-pressure sliding (HPS) is one of the severe plastic deformation (SPD) techniques and it isgaining attention since it is operated under high pressure to reduce fracture and cracking in less ductile
materials [7]. Furthermore, it was found that the strain generated by the HPS process is proportional tothe hardness in a rod sample [8]. Consequently, it can be possible to establish a relationship between theimposed strain and the strengthening effect.
In this study, the HPS process is applied for processing a Mg-Zn-Y alloy to induce kink bands in the
LPSO phase. The formation of kink bands was quantitatively examined with respect to the equivalentstrain and evaluated the strengthening effect via the measurement of microhardness.
The equivalent strain and hardness variations on thelongitudinal cross-section were shown in Fig. 1 (c) and (d),respectively. It appears that the strain is more accumulatedaround the mid-height part on the cross-section and reaches
higher values than those on the top and bottom sides of thecross-section. Accordingly, the hardness variation issimilar to the strain distribution. Formation of kink bands
is observed in the mid-height part of the HPS processed
sample.
References[1] Y. Kawamura et al., Mater. Trans. 42 (2001) 1172–
1176.
[2] K. Hagihara et al., Acta Mater. 58 (2010) 6282–6293.
[3] Yoshimoto, et al., Mater. Trans, 47 (2006) 959–965.
[4] M. Hirano, et al., Mater. Trans, 51 (2010) 1640–1647.
[5]H. Somekawa, et al., Mater. Lett. 304 (2021) 130653.
[6] H. Somekawa, et al., Materialia 12 (2020) 100786.
[7] T. Fujioka, et al., Mater Trans. 50 (2009) 930-933.
[8] Y. Tang, et al., Mater. Sci. Eng. A 748 (2019) 108-118.

-36-

F
Fig. 1. Appearances of grids (a) beforeand (b) after sliding process, (c)distribution of equivalent strain and (d)hardness variation throughout longitudinalcross-section.

Texture evolution and mechanical properties of Mg-9Y-6Zn alloy via vortex extrusion
Daisuke Ando1*, Takumi Tsuji1, Takenori Tanno2, Motohiro Yuasa3,
Hidetoshi Somekawa4, and Yuji Sutou1,51Department of Materials Science, Graduate School of Engineering, Tohoku University,
6-6-11 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579,
2
Research Institute of Electrical Communication, Tohoku University,
2-1-1 Katahira, Aoba-ku, Sendai, Miyagi, Japan 980-8577
3
Department of Mechanical Engineering and Science, Faculty of Science and Engineering,
Doshisha University, 1-3 Miyakodani, Tatara, Kyotanabe, 610-0394, Japan
4
National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, Ibaraki 305-0047, Japan
5
Japan Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku
Sendai, Miyagi 980-8577, Japan Research Center for Structural Materials,*Email:daisuke.ando.c4@tohoku.ac.jp
The authors systematically investigated the microstructure and mechanical properties of alloys
containing LPSO phase by applying various wrought-processing to Mg-9Y-6Zn(at.%) alloy castings,
which are almost a single phase of 18R-type LPSO phase[1]. As a result, kinked deformation could be
introduced into the LPSO phase by all wrought-processing, and the hardness increased with increasing
the introduced equivalent plastic strain. On the other hand, the amount of strengthening varied
depending on the plastic working process when compared at the same amount of equivalent plasticstrain, and it was found that introduction of shear strain from multiple directions was effective. These
results indicate that combined plastic forming by extrusion and torsion is an effective means forstrengthening mechanism by kink deformation.
In this work, the effect of vortex extrusion (VE) on the texture evolution and mechanical properties of
Mg-9Y-6Zn alloy was investigated. The VE is a severe plastic deformation method that imposes highvalues of strain with simultaneous torsion and extrusion of a workpiece. While most of the kink bands
in conventional extrusion (CE) are formed as a jig-zag into the LPSO phase whose a-axis isperpendicular to the ED direction, the kink bands in VE can be also formed as a wavy bent into the
LPSO phase whose a-axis is nearly parallel in the extrusion direction. The mechanical properties of
VEed sample is shown in Fig.2. The yield stress of VEed sample is lower than that of CEed one. On theother hand, the fracture elongation is superior. In my presentation on the day, I would like to discuss therelationships these mechanical properties and texture evolution via VE process.

Fig. 1 Microstructures of as-cast, conventional and vortex extrusion from ED and TD direction (left)
Fig. 2 Nominal compression stress-strain curves of conventional and vortex extrusion (middle)
Fig. 3 Invers pole figures of conventional and vortex extrusion from ED and TD direction and theSchmid factor of basal slip form TD direction (right)
References[1] Hidetoshi Somekawa, Yoshikazu Todaka, Daisuke Ando, Motohiro Yuasa, Materials Letters, 304(2021) 130653.

-37-

~MEMO~-38-

December 13 (Tue.)

4th ~ 5th session-39-

Stretch-induced structural evolution of semicrystalline polymers:
the effects of strain rate
Liangbin Li
National Synchrotron Radiation Lab, University of Science and Technology of China, Hefei
Anhui, 230029

ABSTRACT
Strain rate is an important factor affecting the structural evolution of polymeric materials in bothprocessing and service conditions. In this talk, we present our recent studies on deformationinduced structural evolution of semicrystalline polymers, including polyethylene, polypropylene,poly(1-butene) and PDMS rubber, under wide range of strain rates. Under high strain rate,
hexagonal phase of polyethylene emerges, which normally appears under high pressure. The
crystal transition from form II to form I of poly(1-butene) under quiescent and low strain rate
conditions is changed when high strain rate is loaded, during which melting or disordering of thethermodynamic stable phase form I is observed. The non-equilibrium phase diagram of stretchinduced crystallization and structural transitions of PDMS rubber is also strongly depended on
strain rate. It seems a general rule that high strain rate results in conformational defects in polymer
crystals and consequently brings new phases or different kinetic pathways of structural transitions,which is consistent with the far from equilibrium nature under high strain condition.

Reference
1) Jingyun Zhao, Shengyao Feng, Wenwen Zhang, et al. Strain Rate Dependence of Stretch-Induced
Crystallization and Crystal Transition of Poly(dimethylsiloxane). Macromolecules, 2021, 54, 19,9204-9216.
2) Shengyao Feng, Yuanfei Lin, Wancheng Yu, et al. Stretch-induced structural transition of linear
low-density polyethylene during uniaxial stretching under different strain rates. Polymer, 2021,
226, 123795.

3) Shengyao Feng, Jianhe Zhu, Wancheng Yu, et al. Strain-Rate-Dependent Phase Transition
Mechanism in Polybutene-1 during Uniaxial Stretching: From Quasi-Static to Dynamic Loading
Conditions，Macromolecules, 2022, 55, 2333-2344.

-40-

Deformation Behavior of High-strength Mille-feuille Structured PVDF
Kentaro Mukumoto1, Koji Okuma2, Daisuke Egusa1, Eiji Abe1, and Hiromu Saito *2
1

2

The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, JAPANTokyo University of Agriculture and Technology, Koganei-shi, Tokyo, 184-8588, JAPAN*Email: hsaitou@cc.tuat.ac.jp

We found that strengthening occurred in the mille-feuille structured crystalline polymers such as highdensity polyethylene (HDPE) and poly(vinylidene fluoride) (PVDF) consisting of hard crystalline
lamellar layer and soft amorphous one by heat elongation [1]. In this report, to understand thestrengthening mechanism of the mille-feuille structured crystalline polymers, we investigated thedeformation behavior of PVDF by small-angle X-ray scattering (SAXS).
Anisotropic layer shaped SAXS pattern was observed at the meridian direction in the heat elongated
PVDF (Figure 1). The results suggest the presence of mutually stacked layer structure of crystalline
lamellar layer and amorphous one with periodic distance in which the longitudinal direction of lamellae
is perpendicular to the elongated one. Thus, mille-feuille-like layer structure was obtained by heatelongation of the PVDF film.
Figure 2 shows the stress-strain curves of the unelongated and heat elongated PVDF. Here thestretching direction was parallel to the elongated direction and was perpendicular to the longitudinal
direction of lamellae. The stress increased steeply with strain after the initial increase in the linear region
without fall by yielding. After the linear increase of the stress up to 200 MPa, the increase of the stressbecame smaller. Owing to the continuous increase of the stress without fall, the stress at break of theelongated PVDF obtained by heat elongation at l=300 % was about ten times larger than that of theunelongated one.

Stress (MPa)elongated
direction

250

elongated(l=300%)

200
150
100

unelongated

50
0
0

20

40

60

430

450

Change of long period (%)

Long period of the mille-feuille structure was estimated by the intensity profile of Fig. 1. In Figure 3
is shown the change of long period of the elongated PVDF (l=300%) with tensile strain during stretching.
Here the long period of the stretched specimen was recovered to the unstretched one after releasing in theelastic region while the change remained in the plastic region. It was found that long period increased
steeply with tensile strain in the elastic region and then the increase of the long period became smallerwhen the plastic deformation started to occur. Since the change of the SAXS pattern was slight, the result
suggests that ripplocation occurs in the plastic region. The strengthening of the mille-feuille structured
PVDF might be attributed to the toughness to cause the continuous increase of the stress during stretchingby preventing the fracture of lamellae due to the chain orientation and ripplocation.

Tensile strain (%)
Fig. 2. Stress-strain curves of theunelongated and heat elongated
PVDF.

Fig. 1. SAXS pattern of
the heat elongated PVDF
(l=300%).
Reference[1] T. Murayama, E. Abe, H. Saito, Polymer 236 (2021) 124343.

-41-

30
25
20

plastic
region15
10elastic
region

5
0
0

5

10

15

20

25

30

35

40

Tensile strain (%)
Fig. 3. Change of long periodof the heat elongated PVDF
(l=300%) during stretching.

Effect of Smectic Layer Deformation on Mechanical Properties ofGlassy Liquid Crystal Polymer Fibers
Masatoshi Tokita*, Katsuki Kawahara and Ryoji Suzuki
Tokyo Institute of Technology, 2-12-1 S1-28, Ookayama, Meguro Tokyo 152-8550, JAPAN*Email: tokita.m.aa@m.titech.ac.jp
We determined that the stress response of a glassy smectic liquid crystal (LC) polymer fiber on tensile
deformation was largely affected by the type of pre-deformations of the layers. The LC polymer used herein
was a main-chain type BB-5(3-Me) polyester (Fig. 1), which forms a smectic layer structure at a spacing of d
= 1.6 nm with alkyl chains segregated from biphenyl mesogens [1]. This polyester yielded three types offibers different in smectic layer deformations. Fiber A with smectic layers stacked along the fiber axis was
prepared by pulling the isotropic liquid. Stretching thisfiber in the LC state at a rate of 5% min-1 up to a strainof 80% folded the smectic layers, producing fiber B
with chevron-shaped layers. Further stretching fiber A
Fig. 1. Chemical structure of BB-5(3-Me)
up to a strain of 270% yielded fiber C with smectic
polyester.
layers divided.
These three types of fibers were stretched at a strain
rate of 5% min-1 in the glassy state at 25 °C, and the stress(σ)–strain (ε) curves and X-ray diffraction patterns were
simultaneously measured (Fig. 2). Fiber A exhibited an
initial elastic modulus E = 0.33 GPa and the stress yieldedat ε = 27% increasing σ up to 33 MPa. As the σ increased,
the smectic layers increased the smectic layer spacing (d).
Fiber B was similar to fiber A in the value of E, however,this fiber could be elongated up to ε more than 300%,
maintaining σ = 23 MPa at ε in the range of 100–200%
and increased σ again up to 25 MPa with further
increasing ε to 300%. The smectic layers increased theinclined angles and decreased the d, involving the polymer
chain glided along the chain axis. Fiber C had a greater E= 0.97 GPa and the σ yielded at ε = 32% with a maximum
σ = 82 MPa. This yield stress was greater than that of fiber
A. Fiber C increased the d at a similar rate to fiber A as theε increased, however, fiber C markedly promoted layer
dividing, differing from fiber A. This suggests that Fig. 2. σ–ε curves measured at 25 °C for
fiber A (non-deformed smectic layers),
dividing smectic layers effectively enhances σ to improve
B (folded layers), C (divided layers),
the fiber strength.
and D samples. Fiber D samples were
The mechanical enhancement of the glassy smectic LC prepared by annealing fiber C samples
can be associated with layer division. Fiber D which was at 110 °C for 12 h. The part at smaller εprepared by annealing fiber C in the LC state, had long is enlarged and shown in the inset.
smectic layers, like fiber A, and exhibited σ = 25 MPa and ε= 9% at the yield point. These yield stress and strain weremore than three times smaller than that of fiber C. Similar mechanical strength enhancements by dividing
lamellae have been found for the lamellae of semi-crystalline polyethylene [2] and a liquid crystal block
copolymer [3].
References[1] M. Tokita et al., Macromolecules 37 (2004) 2527–2531.
[2] T. Murayama, E. Abe, and H. Saito, Polymer 236 (2021) 124343.
[3] S. Yagi, M. Oguro, and M. Tokita, Macromol. Chem. Phys. 223 (2022) 2100399.

-42-

Preparation and Mechanical Properties Evaluation of Multilayer Film having
Mille-feuille and Kink Structures
Y. Watanabe1, K. Kano1, A. Iwamura1, A. Ishigami1,2, S. Nishitsuji1,2 and Hiroshi Ito1,2*
Graduate School of Organic Materials Science, Yamagata University, Yonezawa, 992-8510, Japan
2
Research Center for GREEN Materials and Advanced Processing (GMAP), Yamagata University,
Yonezawa, 992-8510, Japan
Email: ihiroshi@yz.yamagata-u.ac.jp

1

A new material strengthening method has been discovered in which kinks are introduced into
Long-Period-Stacking/Ordered (LPSO) structures with hard and soft layer by layer laminated structures
such as mille-feuille to improve mechanical strength in the field of magnesium (Mg) alloys. Although
the mechanism of kink structure in enhancing material properties has not been elucidated, thestrengthening conditions as mille-feuille in the metals were expressed based on the experience. For
enhancement, a continuous periodic structure of hard/soft layered structure is required, and kink
introduction is essential for this structure. To establish the kink strengthening of this hard/soft layered
structure (mille-feuille structure), in this study, we investigated the relationship between themorphological structure of kink and its mechanical behavior in polymers. To expand the kinkstrengthening method into the polymers field, we fabricated a polymer-based mille-feuille material withkink formation and kink strengthening by plastic deformation processing on polymers mille-feuillestructure, referring to the experience-based strengthening.
In this study, polystyrene (PS, PS Japan, modulus of elasticity (GPa): 3.3) was used as the hard layerand styrene-ethylene-butylene-styrene copolymer (SEBS, modulus of elasticity (GPa): <1) as the soft
layer. PS/SEBS (32 alternating layers of two types) multilayer films were produced using a multilayer
co-extrusion machine (Fig. 1). In addition, super multilayer PS/SEBS film (320 alternating layers of two
types) was produced by laminating 10 sheets of 32-layer film and applying heat press processing using aheat press machine. The TEM observation results of the produced mille-feuille structure are shown in
Fig. 2. These images show that the increase in the number of layers (multilayering) has resulted in adecrease in the layer thickness per layer. In addition, the drawing process reduced the difference in layer
thickness in each layer compared to that before drawing. The mille-feuille structure with a layer
thickness so thin that the PS spheres in the microphase-separated structure are regularly aligned (about
300 nm per layer) was fabricated by the stretching process. Various kink formation processes wereapplied to these mille-feuille structures.
By heat treatment and cooling after stretching, a kink structure was formed in both the stretch (MD)and width (TD) directions in the thin PS layer. However, in PS layers with thicker layers (1 ㎛ or more
per layer), cracks were formed that broke without bending. This image suggests that a layer thickness ofabout 500 nm per layer is required for kink formation. However, these kink formations were limited to a
portion of the film. Therefore, we attempted to control the shrinkage of the layer structure by applying
heat treatment to the stretched sample and tried to form kinks in the entire film. The TEM image after
heat treatment shows that shrinking the layer structure above the Tg of PS.

Figure 1 Multi-layer extrusion machine. Preparationof multilayer films of PS(A: hard)/SEBS(B: soft)

Figure 2 TEM observation after uniaxial stretching
and relaxation for PS/SEBS

Acknowledgments: This study was partially supported by JSPS KAKENHI for Scientific Research on
Innovative Areas “MFS Materials Science” (Grant Numbers JP18H05483).

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Large-scale MD simulations of reinforced polyethylene crystals by pre-elongation
Katsumi Hagita1*, Hiromu Saito2, Takashi Yamamoto3, Mamoru Endo4, Daisuke Egusa4, Eiji Abe4
1
Department of Applied Physics, National Defense Academy; Yokosuka, 239-8686, Japan.
2
Department of Organic and Polymer Materials Chemistry, Tokyo University of Agriculture andTechnology; Koganei-shi, Tokyo, 184-8588, Japan.
3
Graduate School of Science and Engineering, Yamaguchi University; Yamaguchi 753-8512, Japan.
4
Department of Materials Science and Engineering, University of Tokyo; Tokyo, 113-8656, Japan.
*
Email: hagita@nda.ac.jp
A new strategy, “nanomosaification,” for toughening semicrystalline polymers is proposed.
Reinforcement of polyethylene (PE) via uniaxial pre-elongation before isothermal crystallization wasreported [1]. Although such a reinforcement was also observed in deformation with rolling with side
constraints and compression [2], we developed uniaxial deformation systems for comparison between
experiments and molecular dynamics (MD) simulations [3]. We confirmed nano-crystal-domain
downsizing in the reinforced PE through transmission electron microscopy, scattering experiments, andultra-large-scale MD simulations as shown in Fig. 1 (upper). The MD simulations revealed thecontributions of tie-chains to downsize nano-crystal-domains, suppress slippage among thenano-crystal-domains, and toughen the specimen. The deformation-enhanced crystallization of thecrowded PE chains was different from the Lauritzen–Hoffman situation and was modeled using theorientation-controlled interconnected nodule model [3]. Figure 1 (lower) shows results of primitive pathextraction [4,5] of amorphous chains (tie-chains). The MD simulations provided direct atomic-levelinsights and confirmed that the formation and working behavior of amorphous and crystal subchainsdepend on the magnitude of pre-elongation. Based on our virtual experiments with cutting tie-chains in
MD simulations, contribution upon reinforcement by tie-chains was confirmed to be much larger thanthat only by the nano-crystal-domain downsizing [3]. Upon “nanomosaification,” the process–structure–property relationships enable the tailoring of monomaterials and recyclability enhancement.

Fig. 1. Cartoon of “nanomosaificaion” in pre-elongate PE crystals (upper) and primitive pathpresentation of tie-chains (lower).
References[1] T. Murayama, E. Abe, H. Saito, Polymer 236 (2021) 124343.
[2] A. Galeski, Prog. Polym. Sci., 28 (2003) 1643-1699.
[3] K. Hagita, H. Saito, T. Yamamoto, M. Endo, D. Egusa, E. Abe, in preparation.
[4] S. K. Sukumaran, G. S. Grest, K. Kremer, R. Everaers, J. Polym. Sci. Polym. Phys. 43 (2005) 917–
933.
[5] K. Hagita, T. Murashima, Polymer 218 (2021) 123493.

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Introduction of millefeuille-like a/b layered structure and investigation of its kinkdeformation behavior in b titanium alloys
1

Satoshi Emura1*, Rintaro Ueji1, Yukiko Ogawa1 and Hidetoshi Somekawa1
Research Center for Structural Materials, National Institute for Materials Science,
1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, JAPAN*Email: EMURA.Satoshi@nims.go.jp

Recently, new type of strengthening mechanism, called ‘kink strengthening’, was found in Mg alloys
with long-period stacking ordered (LPSO) structure [1]. This ‘kink strengthening’ was also found inother materials with layered structure (millefeuille-like structure), such as MAX phase ceramics [2].
In this study, to pursue possibility of kink strengthening in titanium alloys, millefeuille-like a/b layered
structure was introduced in b titanium alloys [3], and compression tests were performed to form kinkdeformation in this layered structure.
b titanium alloy ingots with composition of Ti-12 mass%Mo and Ti-9Cr were prepared through cold
crucible levitation melting (CCLM). CCLM ingots were forged and hot rolled to 6-mm-thickness
plates. Coupons of around 10-mm width and 50-mm length were cut from the hot rolled plates, andthen heat treated at 1173 K for 18 ks in Ar atmosphere followed by water quenching to obtain b single
phase samples with large b grains. Heat treated coupons were cold rolled with the reduction of 5 %.
After cold rolling, plate-like {332}<113> deformation twins, typical deformation twins in b titanium
alloys, were introduced in the coupons. Cold rolled coupons were finally aged in a/b two phase region(973 K for Ti-12Mo and 923 K for Ti-9Cr). After aging, plate-like a phases were precipitated on thetwin boundaries, and alternately stacked millefeuille-like a/b layered structure was obtained.
To introduce kink deformation, compression tests were performed at the temperature range of 473 K
to 673 K. Specimens for compression tests were cut from aged coupons. Compression direction wasparallel to the TD direction of cold rolling. The microstructure after compression tests was observed
optical microscope and scanning electron microscope (SEM). Figure 1 shows the SEM microstructureof 50% compressed Ti-12Mo samples at 573 K. As can be seen in Fig.1, kink deformation of
a/b layered structure was observed.

Fig. 1. SEM image of kink deformation in Ti-12Mo alloy after 50% compression at 573 K.
References[1] K. Hagihara, N. Yokotani and Y. Umakoshi: Intermetallics, 18 (2010) 267276.
[2] D. Matsui, K. Morita, D. Terada, K. Ikeda and S. Miura, Mater. Trans., 63 (2022) 1055-1064.
[3] S. Emura and X. Ji, Mater. Trans., 61 (2020) 856-861.

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Kink deformation and strengthening in an Al-30wt%Ag alloy with mille-feuille structure
fabricated by aging precipitation and subsequent cold-rolling
Daisuke Terada1*, Masayoshi Sakaki1, and Rio Kurisaki1
Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba, 275-0016, JAPAN

1*

Email: daisuke.terada@p.chibakoudai.jp

Materials having “mille-feuille structure” consisting of soft layers and hard layers is expected to
exhibit kink strengthening. In this study, an Al-Ag alloy having late-like precipitates of Ag2Al werefocused to product the mille-feuille structure.
Al (purity of 99.99%) and Ag (purity of 99.9%) were melted and mixed, and Al-30wt%Ag alloy was
obtained by casting. The casted ingots were homogenized at 500 °C for 100 h and deformed by coldroll with 10% of reduction. The deformed alloy was aged at 400°C for 100 h for precipitation of plate-like Ag2Al. Subsequently, the aged alloy was deformed by cold rolling with 80% of reduction.
Mille-feuille structure consisting of Al matrix and deformed Ag2Al was observed in the cold-rolled
sample. The deformed Ag2Al precipitates were parallel to rolling direction (RD). Specimens forcompression test cut from the obtained alloy. Compression test was carried out at ambient temperature.
Compression direction was parallel to rolling direction. A stress-strain curve of the alloy having
mille-feuille structure was shown in Fig.1. In the figure, photos of the specimen at various compress
strains during the test were also shown. It was found that two kink bands were introduced during thecompression test. At first a narrow kink band formed (arrow A) and width of the kink band increased.
Then, the other kink band introduced from left bottom (arrow B) and crossed the first kink band.
Compression stress dropped when a first kink band was introduced, subsequently increased graduallywith growing in width of the kink band. Stress increased when second kink band formed and cross thefirst kink band. The increment of stress was 9.5MPa, which was regard as the amount of kinkstrengthening.

Fig. 1.

(a) The stress-strain curve of the Al-30wt%Ag alloy with mille-feuille structure,and (b)-(f) the photos of specimen at various compression strains.

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~MEMO~-47-

Disclinations: from Theory to PracticeAlexey E. Romanov1,2* and Anna L. Kolesnikova1,3
ITMO University, Kronverkskiy 49, 197101 Saint-Petersburg, Russia
2
Ioffe Physical-Technical Institute RAS, Polytechnicheskaya 26, 194021 Saint-Petersburg, Russia
3
Institute for Problems in Mechanical Engineering RAS, Boljshoy prospekt V.O. 61, 199178
Saint-Petersburg, Russia*
Email: alexey.romanov@niuitmo.ru
1

We present up-to-date information on the properties of disclinations – defects of rotational type, insolids [1]. First, we discuss geometry and nomenclature for straight and circular disclinations
including their main characteristic – Frank vector [2]. Second, we analyze analytical solutions ofisotropic elasticity boundary-value problems for straight wedge disclinations [3]. The considered planeelasticity problems include those for wedge disclinations in uniform or two-phase cylinders, at a freesurface of a half-space, and in a plate of finite thickness [3]. Three-dimensional problems underanalysis deal with wedge disclinations in a bulk sphere or spherical layer or with the defects with thelines being normal to a free surface of a half-space or to surfaces of the plate [3].
Possible applications of the elasticity solutions for wedge disclinations are discussed [1-3]. We
demonstrate that the disclination properties become a controlling factor when considering rotational
plasticity in solids [2], grain boundaries and their junctions in conventional polycrystals andnanostructured materials [4], crack nucleation and initiation of ductile fracture [2], pentagonal rods andicosahedral micro- and nanoparticles [5], amorphous solids and glasses [2], domains, and twins inferroelastic films adjusted to a bulk substrate [6], and defects in graphene and pseudo-graphenes [7,8].
Special attention is paid to the associated with disclinations development of kink bands in layered
structures including LPSO alloys [9]. In this last case, the geometry and energetics of kinking is
discussed in detail.
References[1] A.E. Romanov and A.L. Kolesnikova, Prog. Mater. Sci. 54 (2009) 740-769.
[2] A.E. Romanov and V.I. Vladimirov, in F.R.N. Nabarro ed. Dislocations in Solids,
North-Holland, Amsterdam, 9 (1992) 191-402.
[3] A.E. Romanov and A.L. Kolesnikova, Rev. Adv. Mater. Tech. 3 (2021) 55-95.
[4] A.A. Nazarov, A.E. Romanov, and R.Z. Valiev, Acta Metal. Mater. 41 (1993) 1033-1040.
[5] V.G. Gryaznov et al., Cryst. Res. Tech. 34 (1999) 1091-1119.
[6] A.E. Romanov et al., J. Appl. Phys. 83 (1998) 2754-2765.
[7] A.E. Romanov, M.A. Rozhkov, and A.L. Kolesnikova, Lett. Mater. 8 (2018) 384-400.
[8] N.D. Abramenko et al., Rev. Adv. Mater. Tech. 2 (2020) 9-26.
[9] V.V. Kaminskii et al., Rev. Adv. Mater. Tech. 4 (2022) 15-31.

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Direct observations of kink microstructure in mille-feuille structured Mg alloys
Daisuke Egusa1*, and Eiji Abe1, 2
University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, JAPAN
2
National Institute for Materials Science, 1-2-1 Sengen ,Tsukuba-shi, Ibaraki, 305-0047, JAPAN*Email: egusa@stem.t.u-tokyo.ac.jp
1

Materials with a mille-feuille structure (MFS), which is represented by alternative staking of soft/hardlayers, are strengthened by introducing kink deformations. It is important to clarify the mechanism ofkink deformation for designing materials that effectively exhibit kink strengthening, but the details have
not yet been clarified. We have investigated the microstructures of kink-deformed MFS-type Mg alloys,
including long-period stacking ordered (LPSO) phases, and confirmed that the crystal rotation at thekink boundary (KB) does not always satisfy the lattice correspondence and that the KB is steep at theatomic scale. Phenomenological models of kink deformation are understood as collective rearrangementof dislocations [1] or internal generation of dislocation pairs [2], but it is difficult to understand theformation process only by dislocation motion due to the microscopic characteristics of the KB. In thisstudy, we investigated the kink-deformed microstructure of Mg alloys using electron microscopy toclarify their formation process and features that contribute to the strengthening of the materials.
Nominal compositions of the alloys used in this study were LPSO-type: Mg97Zn1Y2 and MFS-type:
Mg97Zn1Gd2 (at. %), respectively. The alloys were hot extruded to introduce kink deformation withfollowing conditions; extrusion temperature at 623 K, extrusion ratio of 10, and ram speed of 2.5 mm/s.
Samples for TEM/STEM observations were prepared by mechanical polishing and ion milling.
Fig. 1 show HAADF-STEM images and schematic illustrations of defect structures on KBs formed in
the LPSO phase and MFS, respectively. In both cases, KBs withcrystal rotation of a few degrees consist of basal dislocations in theclose-packed structure. In the case of LPSO phase, dislocations
selectively locate in solute-enriched fcc layers, as shown in Fig. 1(b), which leads to changing the stacking sequence from fcc to hcp
as well as decreasing solute concentrations. As a result, nanoscale
hcp-Mg regions are developed on the KB. In the case of MFS,
dislocations form local fcc regions with solute enrichments (Fig. 1(e)) that correspond to nanoscale solute-enriched staking faults(SESF). The observed structures suggest that kink formation
involves structural changes including thermal activation processes(solute diffusion and dislocations climb), which contribute to thestability of KB formed at the high temperature processing.
Fig. 2 shows a three-dimensional KB structure reconstructed by
STEM tomography observations. In the case of MFS, basal
dislocations on KB are always accompanied by solutesegregations, so the bright plate-like contrasts in Fig. 2 (a)correspond to SESFs. Looking carefully, SESFs are separated
along the [0001] direction inside of the sample, as shown in Fig. 2 Fig. 1 STEM images of KB formed in Mg(b), indicating formation of terminated dislocations on KB. In alloys (a-c) LPSO phase、(d-f) MFS
general, terminations of dislocations cause discontinuities ofdeformation, which should be compensated by defects such as
disclinations [3]. The observed defect structure suggests
activations of a structural relaxation different from the one bydislocation motions. In the presentation, we will discuss the detailsof the defect structure examined by STEM and the first-principles
calculations.
References[1] J. B. Hess et al., JOM, 1 (1949) 599-606.
[2] A. N. Stroh et al., Proc Royal Soc Lond, 223 (1954) 404-414.
[3] R. deWit, J. res. Natl. Bur. Stand., A Phys. chem., 77A, 607 (1973).

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Fig. 2 (a-c) 3D reconstructed KB structure
formed in MFS-type Mg alloy.

Thermal stability of the microstructure of dilute Mg alloys prepared by rapid solidified
ribbon-consolidation technique
Daria Drozdenko1, Klaudia Fekete1, Petr Cejpek2, Patrik Dobroň1,
Kristián Máthis1, Michiaki Yamasaki3, Yoshihito Kawamura4
1

Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University,
Ke Karlovu 5, 12116, Prague 2, Czech Republic2
Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University,
Ke Karlovu 5, 12116, Prague 2, Czech Republic
3
Department of Materials Science, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, 860-8555
Kumamoto, Japan
4
Magnesium Research Center, Kumamoto University, 2-39-1 Kurokami Chuo-ku, 860-8555 Kumamoto,Japan*
Email: dorzdenko@kumamoto-u.ac.jp
The thermal stability of the microstructure of dilute Mg alloys prepared by the rapidly solidified
ribbon-consolidation (RSRC) technique has been investigated with respect to alloy compositions. In theas solidified state, the RSRC material has a very fine grain structure with an average grain size about
1 μm. The random orientation of fine grains results in a weak basal texture with a more pronounced
intensity at the (10-10) pole. Moreover, the Mg-Zn-RE (rare earth) alloys are characterized bydispersive Zn- and RE-rich stacking faults formed in basal planes. These microstructure features lead toenhanced mechanical properties, particularly, a superior yield strength of 360 MPa and moderate
elongation of 18%, even in Mg-Zn-RE alloys with low amount of alloying elements (up to 2 at.%).
In order to reveal the thermal stability of such microstructure, isothermal annealing in a range of
300 °C - 500 °C was applied. Scanning electron microscopy (SEM), including backscatter electron
images (BSE) and electron backscatter diffraction (EBSD) techniques, as well as transmission electron
microscopy (TEM) have been used to analyze the microstructure changes. Furthermore, X-ray
measurements were performed for reliable texture analysis. The microstructure was found to be stablewith increasing annealing temperature up to 400 °C. With further temperature increase, the growth of
the grain size and changes in the texture of the alloy, particularly, redistribution of the intensity at the(10-10) pole, has been observed, which can be related to the recrystallization process. The order ofdispersion of the solute-segregated stacking faults was found to be rather independent of the thermal
treatment. In addition, the microstructure development was correlated with the results of the
microhardness measurements.

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Analysis of Kink Formation Behavior in Al/Al2Cu Mille-feuille Structured Alloys
Takayuki Shiraiwa1*, Naoya Hamada1, Fabien Briffod1, Manabu Enoki1, Koji Hagihara2
1
The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
2
Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, Aichi 466-8555, Japan*
Email: shiraiwa@rme.mm.t.u-tokyo.ac.jp

Directionally solidified Al/Al2Cu eutectic alloys have a lamellar structure consisting of a soft Al
phase and a hard Al2Cu phases. It has recently been reported that the introduction of micro kink-bands
in the Al/Al2Cu eutectic alloys improves their strength [1]. It has been suggested that the strengthening
mechanism is affected by the size and spatial distribution of the introduced kink-bands. The introductionof multiple micro kink-bands is necessary to increase the strength, but the mechanism for the formationof such micro kink-bands is not clear. In this study, in-situ surface observations of Al/Al2Cu eutectic
alloys during compression tests were conducted to understand the mechanism of kink band formation.
To quantitatively analyze the microstructural changes before and after the formation of kink bands,
image analysis using the Radon transform was performed on the optical micrographs. This techniqueallowed us to quatitatively evaluate the microstructural changes over a large area (several mm2) withsubmicron spatial resolution and sub-degree rotational resolution without SEM-EBSD analysis. The
results showed that multiple micro kink-bands occurred simultaneously in a single lamellar colony andthat they were aligned in the same orientation. The observed kink-bands are shown in Fig 1 (a). In orderto formulate the relationship between microstructure and kink band formation, we proposed a model topredict the simultaneous formation behavior of kink bands (number of kink bands or kink bands
spacing), as shown in Fig. 1 (b). It is based on a ripplocation model [2]. Comparison with experimental
results of kink-bands spacing showed the validity of the proposed model.

Fig. 1. (a) In-situ observation of micro kink-bands in Al/Al2Cu eutectic alloy, (b) a model of multiple
kink-bands formation based on ripplocation theory.
References[1] K. Hagihara, T. Tokunaga, S. Ohsawa, S. Uemichi, K. Guan, D. Egusa and E. Abe, Int. J. Plast. 158(2022) 103419.
[2] M. W. Barsoum, Front. Mater. 7 (2020) 146.

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Understanding of kink-band formation by means of a rate-independent modelobtained by homogenization of mille-feuille structure
Karel Svadlenka1*, Daria Drozdenko2, Michal Knapek2,
Martin Kružík3, Kristián Máthis2, and Jan Valdman3
1
Kyoto University, Kitashirakawa Oiwakecho, Sakyoku, Kyoto, 606-8502, JAPAN
2
Charles University, Ke Karlovu 5, 121 16, Praha 2, CZECH REPUBLIC
3
Czech Academy of Sciences, Pod vodárenskou věží 4, 182 00, Praha 8, CZECH REPUBLIC*
Email: karel@math.kyoto-u.ac.jp
Structured materials, such as metallic alloys with atomic-scale layers, show peculiar deformation
patterns, which may have significant implications on material properties. In this presentation, we
discuss one possible approach to modeling and understanding of this kind of pattern formation throughthe so-called rate-independent evolution in the variational setting of finite-strain elasto-plasticity [3].
We start with a mathematical analysis of the macroscopic behavior of mille-feuille structured
materials, which is composed by alternating rigid and soft layers. This is done within the mathematicalframework of homogenization via Gamma-convergence [1]. Next, we build a mathematical model of anevolutionary rate-independent system, which reflects the theoretically obtained insights, and study its
mathematical properties. Finally, we perform numerical simulations of this mathematical model andshow that it yields results that are in a good agreement with experimental measurements [2].

Fig. 1. Comparison of numerical simulations and experiment.
References[1] F. Christowiak and C. Kreisbeck, Calculus of Variations 56:75 (2017).
[2] D. Drozdenko, M. Knapek, M. Kružík, K. Máthis, K. Svadlenka and J. Valdman, to appear in Milan
Journal of Mathematics (2022). https://arxiv.org/abs/2207.01986[3] A. Mielke and Tomáš Roubíček, Rate-Independent Systems: Theory and Application, Springer, NewYork (2015).

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Modeling and Numerical Analysis of Kink Deformation based onGeometrical Elasto-Plasticity Theory
1

Sigiet Haryo Pranoto1*, Shunsuke Kobayashi1, and Ryuichi Tarumi1
Osaka University, 1-3 Machikaneyama-cho, Toyonaka-shi, Osaka, 560-8531, JAPAN*Email: sigiet@nlsm.me.es.osaka-u.ac.jp

The long-period stacking ordered (LPSO) has attracted attention due to its excellent mechanicalproperties originating from the kink deformation. This study aims to conduct modeling and numericalanalysis of kink deformation on a three-dimensional continuous medium based on the theory ofgeometric elasto-plasticity [1-3]. Here, we construct the ortho kink and ridge kink models with several
dislocation configurations. We also construct these two models under the influence of shear deformation.
Referring to the geometrical framework, the kinematics are represented as the reference ℛ, intermediateℬ, and current 𝒮 configurations. The total deformation is expressed by the multiplicative decompositionof the deformation gradient; 𝐹 = 𝐹! ⋅ 𝐹" . For a given dislocation density, we calculate the plastic
deformation gradient 𝐹" by solving the weak form of the Cartan first structure equation so that theintermediate configuration is obtained. The elastic deformation gradient 𝐹! is obtained by minimizing
the strain energy functional. Then, we solve the variational problem numerically using the finite element
method. The ortho kink is modeled by a pair of kink interfaces containing an array of edge dislocations
and the ridge kink is modeled by a combination of vertical and inclined kink interfaces.
The present analysis showed that the deformation agrees qualitatively with the experimental results.
In the ortho kink model, the deformation exhibits a sharp inflection at the kink interface where the edge
dislocation array is placed. While the ridge kink model shows sharp extrusions on the top and bottom
surfaces of the domain where the ridge kink structure is placed. Note that, the deformation is highly
localized around the kink structure. We also investigated the internal stress distribution for these twomodels. In the ortho kink model, when the kink interface penetrates and reaches the free surface, stressconcentration could not be confirmed. However, when the kink interface does not penetrate the stress
distribution appears at the tip of the kink interface. This is believed due to the presence of a disclination.
On the other hand, the ridge kink model shows a low-stress field because at the tip of the ridge kinkstructure the disclination cancels each other out. The last thing we need to address is strain energy. We
reported that the strain energy is higher after the shear deformation is applied. Here, we would like toclarify the effect of the kink interface length for these two models on the deformation and the stressfield. Then, we will discuss the strengthening mechanism due to the kink structure.

Fig. 1(a) and (b) show the dislocation configurations for the ortho kink and ridge kink models. (c) and(d) show stress components 𝜎#$ for the ortho kink and ridge kink models, respectively.
References[1] A. Yavari and A. Goriely, Arc. Rat. Mech. Ana. 205 (2012) 59-118.
[2] S. Kobayashi and R. Tarumi, Bulletin of the JSME. 87 (2021) 894.
[3] S. Kobayashi and R. Tarumi, Bulletin of the JSME. 87 (2021) 896.

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~MEMO~-54-

December 14 (Wed.)

6th ~ 7th session-55-Crystal Plasticity-Based Prediction of Forming Limit Diagrams:
Application to Magnesium Alloys
Sean R. Agnew* and Michael A. Ritzo
The University of Virginia, Charlottesville, VA, 22904-4745, USA*Email: agnew@virginia.edu
There has been much study focused on developing an improved understanding of the limited cold
formability and, conversely, excellent warm formability of Mg alloys. Countless attempts have been madeto improve the cold ductility of Mg via alloying, texture engineering, and microstructure control (e.g.,grain size reduction). Many of these efforts have been accompanied by polycrystal plasticity modeling toprovide mechanistic understanding, and this has often highlighted the potentially critical role of particulardislocation slip or deformation twinning mechanisms.
In the present research, the potentially important role of diffusion-controlled mechanisms, namely
dislocation climb is reconsidered. The present authors recently reported that a new crystal plasticity model(VPSC-CLIMB), which explicitly accounts for the kinematics of dislocation climb, enables a moreaccurate description of strain anisotropy and texture evolution within the strain rate and temperature
regime in which the ductility of Mg alloys can be excellent. [1] Perhaps more surprisingly, the results
suggest that the climb of basal dislocations with <a>-type Burgers vectors accommodates a significant
fraction of the strain under these conditions. The constitutive parameters employed in the modeling wereobtained by a genetic algorithm (GA) based optimization of an objective function which involved
minimization of the residual difference between measured and predicted crystallographic textures.
In the present research, this VPSC-CLIMB model is integrated with the Marciniak–Kuczynski (M–K)
approach for forming limit curve (FLC) prediction. The approach allows for the incorporation of
crystallographic texture-induced anisotropy and the evolution of the same during the deformation.
Previous attempts at such polycrystal plasticity-informed FLC prediction occurred at a time when few
experimental assessments had been made. [2] Since that time, the FLCs of numerous Mg alloys withvarious textures and microstructures have been assessed. [e.g., 3] These assessments include
measurements of the crystallographic texture prior to and after forming along drawing-, plane strain-, andstretching-type strain paths. These new data provide a more critical validation of the polycrystal modelbased FLC predictions and further highlight the importance of dislocation-climb accommodated plasticity
under conditions when Mg alloys are considered formable. Finally, the modeling effort provides possible
explanations for some of the rather strange behaviors exhibited by some Mg alloys, such as lower
formability along the stretching direction as compared to that observed along the plane strain (FLC0)
condition.
References[1] M.A. Ritzo et al. Mater. Sci. Eng. A 839 (2022), 142581.
[2] C.J. Neil and S.R. Agnew, Int. J. Plasticity, 25(3) (2009) 379-398.
[3] J. Bohlen et al. Metals, 8(2) (2018) 147.

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Influence of electrochemical and geometrical heterogeneities on corrosion behaviour of
LPSO phase-containing Mg-Y-Zn alloys
Michiaki Yamasaki1, *, Zhiming Shi2, Andrej Atrens2, and Yoshihito Kawamura1
1
Magnesium Research Center, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 8608555, Japan
2
School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, Brisbane, Qld
4072, Australia*
Email: yamasaki@gpo.kumamoto-u.ac.jp
Magnesium alloys have attracted considerable attention as promising for light-weighting applications.
In addition, Mg alloys are suitable for metallic implants such as stents and bone screws that require biocompatibility and bio-absorbability. However, commercially available Mg alloys manufactured byconventional ingot metallurgy have strength, ductility, and corrosion resistance inferior to commercial Al
alloys. Thus, the applications of Mg alloys can be further extended by the development of Mg alloys with
better mechanical properties and better corrosion resistance.
Excellent mechanical properties have been provided by the development of the high-strength Mg-ZnY alloys with long-period stacking ordered (LPSO) phases[1-3]. These LPSO-typed Mg-Y-Zn alloys arepromising, novel, high-strength wrought alloys. The multimodal microstructure of the extruded LPSOtype Mg-Y-Zn alloys comprises three distinct regions: a dynamically recrystallized (DRXed) a-Mg grain
region with random orientation; a worked a-Mg grain region with a strong fiber-texture of<101"0>//extrusion direction (ED), and a worked LPSO phase grain region with the strong fiber texture.
The fine DRXed a-Mg grains contribute toward the improvement in the ductility of the alloy, whereas
the coarse worked a-Mg and LPSO grains contribute toward the mechanical strength of the alloy[4]. The
LPSO phase provides strengthening because of its unique anisotropic plastic deformation behavior which
originates from its unique long-period/chemical ordered structure.
The corrosion performance of these LPSO-typed Mg alloys is mainly determined by two factors. The
LPSO phase increases the corrosion rate of the alloy, by micro-galvanic acceleration for the corrosion of
the a-Mg matrix, because the 18R-structured LPSO phase contains high concentrations of Y and Zn. In
addition, corrosion is induced by the variations in crystal orientation. In this study, the influence of thedispersed LPSO phase and the multimodal microstructure on the corrosion behavior of the a-Mg/LPSO
two-phase wrought alloys has been clarified.
The extruded Mg-Y-Zn alloy showed orientation dependent corrosion behavior, the longitudinal
section exhibited a higher corrosion rate than the transverse section[5]. The orientation dependence wasattributed to the varying in-plane atomic densities of the crystallographic planes on the longitudinal andtransverse cross sections. The LPSO phase was the cathode and galvanic corrosion occurred in theadjacent a-Mg matrix. In this study, we have also attempt to improve corrosion resistance of the LPSOtyped Mg alloys. The Al alloying into the Mg-Y-Zn alloy facilitated the formation of a protective surface
film, which decreased the corrosion rate in spite of geometrical and electrochemical heterogeneities.
References[1] Y. Kawamura et al. Mater. Trans. 42 (2001) 1172-1176.
[2] Y. Kawamura et al. Mater. Trans. 48 (2007) 2986-2992.
[3] K. Hagihara et al. Acta Mater. 58 (2010) 6282-6293.
[4] M. Yamasaki et al. Acta Mater. 59 (2011) 3646-3658.
[5] M. Yamasaki et al. Corros. Sci. 200 (2022) 110237.

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Effects of Additional Deformation and Heat Treatment on Kink Bands on the surface of
LPSO-type Mg85Y9Zn6 Directionally Solidified Alloy Thin Plates
Mayumi Suzuki1*, Keisuke Hio,1,2, Kakeru Sato1,3, and Yusuke Ichikawa1,4
Department of Mechanical Systems Engineering, Faculty of Engineering,
Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama, 939-0398 Japan
2
Undergraduate Student, Toyama Prefectural University
3
Undergraduate Student, Toyama Prefectural University (Now with TOTEC Amenity Limited)
4
Graduate Student, Toyama Prefectural University*
Email: smayumi@pu-toyama.ac.jp
1

Mg-TM-RE (TM: transition metals, RE: rare earth element) based alloys containing the long period
stacking ordered (LPSO) phase, a type of mille-feuille structure, have been investigated by many
researchers for their high mechanical properties [1] and unique crystalline structures.
LPSO-typemagnesium alloys significantly increase their strength by plastic deformation and this phenomenon is
explained by the formation of kink bands, which act as the strong obstacles to the primary slip ofdislocations (basal a-dislocation slip) [2]. On the other hand, the response of kink bands introduced
into a material to subsequent plastic deformation remains unresolved and requires experimental
investigation. Furthermore, effects of heat treatments on kink strengthening are not well understood.
In this study, effects of additional plastic strain on the character of kink band and heat-treatment on thekink strengthening were investigated in LPSO-Mg85Y9Zn6 directionally solidified (DS) alloy.
The material used in this investigation is a DS LPSO type Mg85Y9Zn6 alloy. Thin specimens were cut
from parallel to the solidification direction and adjusted to a thickness of approximately 100~250 µm.
The thin specimen was then placed between the indium plate and the round bar and bending strain wasapplied by pressing the thin specimen against the round bar with the indium plate. Many wedge-typekink bands with undulations were observed on the surface of compression-side after the bending test.
After observing these kink bands, the bending direction was reversed (2nd bending) for the same sample
and the observation was carried out again. For a part of specimens, heat treatment was applied before
the 2nd bending test.
Microstructures were observed by using transmission electron microscope(TEM) and analyzed by electron backscatter diffraction pattern (EBSD) measurements in a field-emission
type scanning electron microscope (FE-SEM).
From optical microscopic observations, most of kink bands of several tens of microns or more did not
expand/shrink after additional bending deformation at room temperature. On the other hand, the degreeof surface undulation caused by the wedge-type kink bands tended to decrease after the 2nd bending test.
EBSD analysis revealed that the rotation angle of a kink boundary decreased compared to that after the
1st bending test. Furthermore, when further plastic deformation was applied after kink band formation,
the strain tended to concentrate near the kink band.
Investigation of the Vickers hardness of thespecimens after bending deformation showed higher values around the kink band than in the matrix.
The Vickers hardness around the kink band increased significantly after heat treatment at 500-650 K.
However, after 2nd bending test, the hardness around kink bands increased only slightly and/or decreased.
It was suggested that Vickers hardness around the kink band tends to depend on the rotation angle of its
boundary.
References[1] Y. Kawamura K. Hayashi, A. Inoue, and T. Masumoto: Mater. Trans., 42 (2001), 1172-1176[2] K. Hagihara, Z. Li, M. Yamasaki, Y. Kawamura, T. Nakano: Acta Mater., 163 (2019), 226-239
Acknowledgments
This work was supported by JSPS KAKENHI (Grant-in-Aid for Scientific Research on Innovative
Areas (Research in a proposed research area) "Materials Science on mille-feuille structure (MFS)")
Grant Numbers JP18H05478, JP19H05134, JP21H00105.

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Microstructure and Deformation Behavior of BCC-V/MAX two-phase alloys
Seiji Miura1*, Hiroto Kudo2, Shiho Takebe3, Nobuaki Sekido4 and Ken-ichi Ikeda1
1 Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo 060-8628, Japan,
2 Graduate Student, Hokkaido University, kita13 Nishi8, Kita-ku, Sapporo 060-8628, Japan
3 Undergraduate student, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo 060-8628, Japan,
4 Graduate School of Engineering, Tohoku University, Sendai 980- 8579, Japan,*
Email: miura@eng.hokudai.ac.jp
Introduction
Max phases have attracted attentions because it shows excellent properties such as high strength, highmelting point and low density [1]. The present authors have conducted a study to obtain a new class ofmille-feuille materials by attaining lamellar structure composed of the BCC-V based materials and Max
phase V2AlC. It was already found that BCC-V matrix alleviate the delamination tendency of MAX phaseduring plastic deformation even at relatively lower temperatures. In this study effect of various quaternary
elements on the stabilization of lamellar structures is investigated, and also the deformation behavior isstudied.
Materials and Methods
Based on the V-Al-C ternary phase diagram [2], alloy composition with and without quaternary additives
such as Cr, Ti, Mo and W were determined and ingots were prepared using an Ar-arc melting machine.
A part of ingots sealed in evacuated silica tubes was subjected to a heat-treatment at 1473 K for 1 week.
Microstructure observation using FE-SEM and WDS analysis for determining the composition of eachphase was conducted, and the crystallographic orientation relationship between BCC-V and MAX phase
was investigated using EBSD. Compression tests are also conducted to understand its deformation
behavior and kink formation tendency.
Results and Discussion
It was confirmed that the alloys with and without the heat-treatment have two-phase microstructure,
however, plate-like V2AlC-MAX phase in as-cast ternary and some quaternary alloys spheroidized during
the heat-treatment. The MAX phase in alloys with W keeps its plate-like shape even after the heattreatment, resulting in fine mille-feuille microstructure. The tendency can be explained in terms of thesolubility (partitioning) ratio of quaternary elements in BCC V and Max phases, which control the latticemismatch through the effect of quaternary elements on lattice constant ratio between BCC and MAX
phases. Kink formation was also found in the sample during the compression tests.
Acknowledgement
This work was supported by a grant from JSPS KAKENHI for Scientific Research on Innovative Areas“MFS Materials Science (Grant Numbers JP18H05482).
References[1] M. W. Barsoum and T. El-Raghy, Am. Sci., 89 (2001) 334-343.
[2] B.Hallstedt, CALPHAD, Computer Coupling of Phase Diagrams and Thermochemistry, 41(2013),
156-159.

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Observation of as-cast and extruded Mg97Zn1Y2 alloys by neutron diffraction and thermal
dilatometer measurement
Kazuya Aizawa1*, Stefanus Harjo1, Wu Gong1 and Takuro Kawasaki1
J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki,319-1195, Japan*
Email: aizawa.kazuya@jaea.go.jp

1

From the viewpoint of acquiring the basic properties of the two-phase Mg-based LPSO alloy, typically
Mg97Zn1Y2 [1], the thermal response of the as-cast alloy, and the extruded alloy with an extrusion ratioof 10, which is introduced kink structure, was analyzed by using neutron diffraction and thermal
dilatometer in order to investigate the effect of kink structure on the thermal properties. In thermal
expansion measurements to observe macroscopic changes of the alloy, the Mg-phase of the extruded alloyis less than that of pure-Mg reported previously. This behavior of the Mg phase in the extruded alloy
seems to be due to the introduction of kinks of 18R LPSO phase. Fig. 1(a) shows the temperaturedependence of (1010) and (0002) in the atomistic level of -Mg phase in the as cast and extruded
Mg97Zn1Y2 alloys with downward convex quadratic fitting functions. From the figure, the change of the
extruded alloy is more moderate. This is consistent with macroscopic thermal dilatometer result.
Mg97Zn1Y2 alloy consists of volume fractions of 75% -Mg phase and 25% 18R LPSO phase. Becauseof this less volume fraction of LPSO phase, the detectable LPSO diffraction peaks are quite limited. We
used the (42210) and (4228) peaks of 18R LPSO phase [2] for the analysis in this study. Fig.1(b) shows
the temperature dependence of d-spacing of (42210) plane of 18R LPSO phase in the Mg97Zn1Y2 alloy.
In the case of extruded alloy, the temperature dependence of the (42210) plane of the LPSO phase in the
Mg97Zn1Y2 alloy is suppressed at higher temperature.

d (1 0 -1 0) (Å)

d (0 0 0 2) (Å)

2.430
Mg97Zn1Y2

2.425

as cast, axial
as cast, radial
extrusion, axial
extrusion, radial

2.420
2.415
2.410
2.405
2.400

0

100
200
300
Temperature (℃)

400Fig. 1. (a) the temperature dependence of d-spacing of (1010) and (0002) planes in the atomistic
level of -Mg phase in the Mg97Zn1Y2 alloy with quadratic fitting functions. (b) the temperaturedependence of d-spacing of (42210)plane of LPSO phase in the Mg97Zn1Y2 alloy.
References[1] Kawamura, Y., Hayashi, K., Inoue, A., Masumoto, T., Mater. Trans. 42(2001)1172–1176.
[2] Abe, E., Ono, A., Itoi, T., Yamasaki, M., Kawamura, Y., Phil. Mag. Lett., 91(10)(2011)690-696.

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~MEMO~-61-

Synergetic kinking and twinning in an Mg-Zn-Y-Zr alloy
with intragranular LPSO structures
Xiaohong Shao1*, Zhenzhen Peng2, and Xiuliang Ma1
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academyof Sciences, 72 Whenua Road, 110016 Shenyang, China
2
Hebei Key Laboratory of Material Near-Net Forming Technology, School of Materials Science andEngineering, Hebei University of Science and Technology, 050018 Shijiazhuang, China*Email: xhshao@imr.ac.cn

1

Deformation kink is one of the important strengthening mechanisms for the magnesium (Mg) alloys
containing long-period stacking ordered (LPSO) phase [1], while deformation twin is generally
suppressed by the thick LPSO structure. The synergistic effect between the deformation kink and the twinneeds further understanding.
To optimize the mechanical properties of the Mg alloy with LPSO structures, we simultaneously
introduced kink and twin in the Mg-Zn-Y-Zr alloy featuring the intragranular LPSO phase and free grainboundary LPSO phase by homogenization [2]. We unraveled the corresponding strengthening andtoughening mechanisms through transmission electron microscopy characterization and theoreticalanalysis. The high strength and good plasticity of the homogenized alloy benefit from the synergistic
deformation mechanism of multiple kinking and twining in the grains. And the activation of kinking andtwinning depends on the thickness of LPSO lamellae and their relative spacing. These results may shedlight on optimizing the design of Mg alloys regulating the microstructure of LPSO phases.

Fig. 1. (a) STEM and (b) TEM images of two grains in the homogenized sample after compressive
deformation. One can find that kinks, micro-kinks, and twins, as shown by the red, green, and yellow
arrows, respectively, coexist in the grains in the homogenized alloys.
References[1] K. Hagihara, Z. Li, M. Yamasaki, et al. Acta Materialia 163 (2019) 226-239.
[2] Z. Z. Peng, X. H. Shao, et al. Journal of Magnesium and Alloys (2022) online.

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Kink-band formation in Mg/LPSO two-phase alloys
Toko Tokunaga1*, Koji Hagihara1, Michiaki Yamasaki2, Tsuyoshi Mayama2, Yoshihito Kawamura2, andTakayuki Nakano3
1
Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, Aichi, 466-8555, JAPAN2
Magnesium Research Center & Department of Materials Science, Kumamoto University, 2-39-1
Kurokami, Chuo-ku, Kumamoto 860-8555, JAPAN
3
Division of Materials and Manufacturing Science, Graduate School of Engineering,Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, JAPAN*Email: tokunaga@nitech.ac.jp
The development of lightweight high-strength alloys has been gaining attentions because of increasingawareness of reduction in CO2 emissions to mitigate global warming problems. Mg alloys have the lowest
density among all structural materials, and they have been expected to solve the environmental issues.
However, the strength of the Mg alloys must be improved for practical applications [1, 2]. Recently, it
was reported that the superior mechanical properties were achieved in the Mg-Zn-Y ternary alloys withlong-period stacking ordered (LPSO) phase. Although the strengthening mechanism of the alloys is
considered to be related to the strong plastic anisotropy of the LPSO phase, the detailed mechanism has
not fully clarified yet. In the present study, to investigate the controlling factors of the mechanicalproperties of Mg/LPSO two-phase alloys from a basic point of view, the influence of the volume fractionof the LPSO phase on the mechanical properties of Mg/LPSO two phase alloys was examined withdirectionally solidified (DS) alloys. Mg/LPSO single-phase and two-phase alloys of Mg85Zn6Y9,
Mg89Zn4Y7, Mg92Zn3Y5, Mg94Zn2Y4, and Mg97Zn1Y2 (at%), were prepared by induction melting followedby the directional solidification with Bridgman technique in an Ar gas atmosphere at a growth rate of 10
mm/h. The volume fractions of the alloys were measured to be 100, 86, 61, 39, 26 vol.%, respectively.
The microstructures were observed by optical microscope and scanning electron microscopy (SEM), andcompression tests were conducted at an initial strain rate of 1.67 × 10−4 s−1 and at room temperature, 200,
300 and 400 oC. In the compression tests, the loading axes were set at the direction parallel to the growth
direction, and the direction inclined at 45o to the growth direction in the DS process.
From the microstructure observation, in both the LPSO single-phase alloy and the Mg/LPSO two-phasealloys, it was found that the platelet LPSO phase grains and the basal plane of the LPSO phase were wellaligned parallel to the growth direction. Although the LPSO phase is basically considered as an effective
strengthening phase in Mg alloys when stress is applied parallel to the growth direction, the alloys
exhibited a nonmonotonic increase with an increase in the volume fraction of the LPSO phase. The highest
strength was obtained in the Mg/LPSO two-phase alloys containing 61-86 vol.% of the LPSO phase. From
the observation results of the deformation microstructure, it was clarified that this anomalous variation in
the yield stress was due to the change in the formation stress of kink bands, which varied with the
thickness of the LPSO-phase grains. Furthermore, the coexistence of Mg phase in the two-phase alloys
induced the homogeneous formation of kink bands, whose boundaries can act as effective obstacles
against further motion of the basal dislocation. This is referred to as the “kink-band strengthening” [3].
Activation of the kink-band strengthening was evaluated by specially-designed compression tests, i.e.,“double compression tests”. The double compression tests are composed of two compression tests;
specimens were firstly compressed at 0o to the growth direction to induce kink bands, and secondly, thespecimens were compressed at 45o.The yield stress of all the single-phase and two-phase alloys increased
from the conventional compression tests loaded at 45o to the growth direction. The results demonstrated
that microstructural control is significant in the Mg/LPSO two-phase alloys to optimize mechanicalproperties.
References[1] F. Pan, et al., J Mater Sci Technol. 32 (2016) 1211-1221.
[2] Y. Kawamura, et al., Mater Trans. 42 (2001) 1172-1176.
[3] K. Hagihara, et al. Acta Mater. 15 (2019) 226-239.

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Crystal plasticity analysis of kink band formation in Mille-feuille structure
1

Tsuyoshi Mayama1*, Koji Hagihara2, Daisuke Egusa3, and Eiji Abe3
Kumamoto University, 2-39-1, Kurokami, Chuo-ku, Kumamoto, 860-8555, JAPAN2
Nagoya Institute of Technology, Gokiso, Nagoya, Aichi, 466-8555, JAPAN3
University of Tokyo, Tokyo 113-8656, JAPAN*
Email: mayama@kumamoto-u.ac.jp

Kink banding is a type of localized deformation modes where large crystal rotation within the band
region is accompanied [1]. In several metallic materials, possible contributions of formation of kinkbands to strengthening is suggested [2-4]. Magnesium (Mg) alloys containing Long-Period Stacking
Order (LPSO) phase show significant improvement of mechanical properties owing to metal forming
processes where a number of kink bands are formed [2]. Al-Cu eutectic alloys with fine kink bands also
show high strength at room temperature strength [3, 4]. Especially, the latter case indicates possible
alloy design where frequency of kink band formation and strength are deliberately controlled. To
achieve such alloy design, it is necessary to understand underlying mechanism of kink band formationin eutectic alloys consisted of hard and soft lamellar phases. In this study, we investigate active
deformation mode in Al-Cu eutectic alloys during kink banding under compressive loading via
numerical calculations by crystal plasticity finite element method [5, 6]. In order to clarify the effective
parameters on kink band formation, systematic parameter study was performed by changing criticalresolved shear stresses in each phase, volume fraction of each phase, and distribution of defects. Figure
1 shows a typical calculated result where kink band is formed during compressive loading. The
distribution of equivalent strain indicates that larger plastic strain is accumulated in softer Al phase
while both phases show significant bending regardless of much smaller amount of equivalent strain in
Al2Cu phase compared with Al phase.

Fig. 1. Calculated result of kink band formation in Al-Cu eutectic alloy model.
References[1] Asaro and Rice, J. Mech. Phys. Solids, 25 (1977) 309-338.
[2] Hagihara et al., Acta Materialia, 163 (2019) 226-239.
[3] Hagihara et al., Mater. Sci. Eng. A, 825 (2021) 141849.
[4] Hagihara et al., Int.J. Plasticity, 158 (2022) 103419.
[5] Mayama et al., Mater. Trans., 56 (2015) 963-972.
[6] Yamasaki et al., Mater. Sci. Eng. A, 819 (2021) 141466.

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On Scale-Free Nature of Kink Formation/Strengthening based on FTMP
1

Tadashi Hasebe* and Kota Mizutani2
Kobe University, 1-1 Rokko-dai, Nada, Kobe, Japan
2
Graduate School of Kobe University, ibid.
*
Email: hasebe@mech.kobe-u.ac.jp

Scale-free relationships, together with the associated specific return maps, have been experimentally
reported for AE characteristics of deforming LPSO-Mg DS sample both before and after kink formation
stages [1], although their roles and significance have not been disclosed hitherto. FTMP (Field Theory ofMultiscale Plasticity) [2,3], on the other hand has been successfully applied to reproduce the kinkformation processes when combined with crystal plasticity-based finite element (CP-FE) simulation [4,5].
This study makes a primary series of attempts to clarify the above by means of FTMP-based CP-FE
simulations assuming a priori the experimentally measured AE characteristics, as shown in Fig.1(left),
where the interaction field formalism [6] and the flow-evolutionary law in FTMP are utilized. Thus
enriched simulation results are also compared in Fig.1(right) with those in the previous counterparts.
Demonstrated preliminarily are either changes in the kink morphologies or an improvement of the energy
return map characteristics. Starting with this, detailed contributions of the enrichment are further
investigated.

Fig. 1. Overview of the enrichment process, together with preliminary simulation results (rotation angle
contour and the associated return map), comparing with the previous results.
References[1] Aizawa K. et al., (2019), Proc. JMMI
[2] Hasebe, T., (2006), ‘‘Multiscale Crystal Plasticity Modeling based on Field Theory,” CMES, 11-3,
145-155.
[3] Hasebe, T., Sugiyama, M., Adachi, H., Fukutani, S., Iida, M., (2014), “Modeling and Simulations ofExperimentally-Observed Dislocation Substructures Based on Field Theory of Multiscale Plasticity(FTMP) Combined with TEM and EBSD-Wilkinson Method for FCC and BCC Poly/Single Crystals,”
Mater. Trans., 55-5, 779-787.
[4] Nawa, Y. and Hasebe, T., (2021), “FTMP-based Kink Deformation and Strengthening Mechanisms
for Mille-feuille Structures,” Maters. Sci. Forum, 1016, 1019-1023.
[5] Nawa, Y. and Hasebe, T., (2021), “FTMP-based Kink Deformation and Strengthening Mechanisms
for Mille-feuille Structures,” Int. J. Multiphysics, 15-3, 325-348.
[6] Hasebe, T., (2009), “Interaction Fields based on Incompatibility Tensor in Field Theory of PlasticityPart I: Theory,” Int. Multiscale Mech., 2-1, 1-14

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Mesoscale modeling of system of planar wedge disclinations and edge dislocations via the
Airy Stress Function method1

Pierluigi Cesana1*
Institute of Mathematics for Industry, Kyushu University, 744 Motooka Nishi-ku, Fukuoka, 819-0395,
Japan*
Email: cesana@math.kyushu-u.ac.jp

I will describe recent results on the modeling and analysis of finite systems of planar wedge
disclinations and edge dislocation via a new energy minimization principle for the elastic energy of thesystem.
Planar wedge disclinations are angular mismatches appearing at the nano-scale in a crystal lattice
entailing a violation of rotational symmetry [1,4]. Together with dislocations, disclinations are observedin crystal plasticity [2] and in Shape-Memory Alloys undergoing the austenite-to-martensite
phase-transition [3]. We introduce a novel mathematical formulation for the elastic energy of finite,
isotropic systems of planar wedge disclinations and edge dislocations [6]. We operate in the regime ofplanar mechanical strains and linearized kinematics. In our theory disclinations and dislocations emerge
as the solutions to minimization problems for isotropic mechanical energies under the constraint ofkinematic incompatibility. As it is customary when working with 2-dimensional geometries inlinearized elasticity, we write the mechanical equilibrium problem by introducing the Airy potential of
the system, for which we construct a new variational formulation in the context of incompatible
elasticity and for a non-simply connected domain. Our main result is the exact characterization of theenergetic equivalence of a disclination dipole and an edge dislocation for various configurations
identified by suitable rescaling of the energy of the system. By adopting the core-radius regularization
approach [7] we show that, as the core radius vanishes, the (renormalized, rescaled) energy of adisclination dipole converges to the (renormalized, rescaled) energy of an edge dislocations.
Acknowledgments. This work is supported by JSPS Innovative Area Grant JP21H00102 andJP19H05131.

References[1] V. Volterra, Annales scientifiques de l’École Normale Supérieure 24 (1907)401–517.
[2] K. Hagihara, N. Yokotani, and Y. Umakoshi, Intermetallics 18(2) (2010) 267–276.
[3] K. Bhattacharya, Oxford University Press (2003).
[4] P. Cesana, P. van Meurs, ESAIM COCV 27, 23 (2021).
[5] P. Cesana, F. Della Porta, A. Rueland, C. Zillinger, and B. Zwicknagl, Archive for Rational
Mechanics and Analysis 237(1) (2020) 383–445.
[6] P. Cesana, L. DeLuca, M. Morandotti, ArXiV 2207.02511 (2022).
[7] P. Cermelli, G. Leoni, SIAM SIMA 37 (2005) 1131—1160.

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Effect of Kink Band Spacing on Kink Strengthening in LPSO-type Magnesium Alloy
1

Yuichi Tadano1* and Kaito Kimura1
Saga University, 1 Honjo-machi, Saga 840-8502, JAPAN*
Email: tadano@me.saga-u.ac.jp

Magnesium alloys with the long period stacking order (LPSO) structure show the superior strengthand are expected as the next generation structural material. In the LPSO-type magnesium alloy, apeculiar deformation called kink plays an important role and induces a drastic strengthening of materials.

Therefore, understanding the kink strengthening phenomena is essential. Kink takes various
morphologies, and it may affect kink strengthening. Additionally, multiple kink bands sometimes exist
in proximity. Therefore, the spacing of kink bands may also be important. Kink band causes the strain
gradient around the band. The higher-order gradient crystal plasticity [1] is an efficient way to represent
the strain gradient effect in the crystalline scale. In this model, an additional governing equation
expressing the dislocation density filed is introduced, and both the displacement and dislocation density
fields can be solved simultaneously.
In this study, a higher-order gradient crystal plasticity analysis is conducted to evaluate the stressfield around kink band to understand the strengthening mechanism due to kink. The finite element
method sometimes provides an improper solution in the higher-order gradient crystal plasticity analysis[2]; therefore, the reproducing kernel particle method (RKPM) [3,4], which is a kind of meshfree
method, is introduced into the higher-order gradient crystal plasticity analysis. A numerical analysis of a
specimen with two kind bands is demonstrated, and the effect of kink spacing is quantitatively
investigated. The present result suggests that there are three mechanisms in kink strengthening, that is
texture, defect and neighboring strengthening shown in Fig. 1. The amplitude of neighboring
strengthening depends on the kink spacing, and closer kink bands give a higher kink strengthening.

Fig. 1. Contributions of three strengthening mechanisms to kink strengthening with respect to kink angle.
References[1] M. Kuroda and V. Tvergaard, J. Mech. Phys. Solids, 56 (2008), 2573-2584.
[2] M. Kuroda, Int. J. Solids Struct., 48 (2011), 3382-3394.
[3] J.S. Chen et al., Comput. Methods Appl. Mech. Engrg., 139 (1996), 195-227.
[4] J.S. Chen et al., Int. J. Numer. Mech. Engng., 50 (2001), 435-466.

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~MEMO~-68-

December 14 (Wed.)

Poster session-69-

Toughening of the LPSO-type Mg-Zn-Y-Al RS P/M alloys
Soya Nishimoto1*, Ayami Yoshida1, Shin-ichi Inoue2, Michiaki Yamasaki2, and Yoshihito Kawamura2
1Graduate Student, Graduate School of Science and Technology, Kumamoto University
2Magnesium Research Center/Department of Materials Science, Kumamoto University
Email: s.nishimoto@msre.kumamoto-u.ac.jp
Mg alloys are attractive structural materials for use in transportation vehicles owing to their low
densities. However, current use is limited due to low strength of Mg alloys. Recently, LPSO-type MgZn-Y alloy having excellent mechanical property was developed [1-3]. Especially, the Mg-Zn-Y-Al rapidly
solidified (RS) P/M alloys through non-equilibrium processing exhibit high strength, excellent fatigue
properties, and high corrosion resistance [4-6]. Therefore, the Mg-Zn-Y-Al RS P/M alloys could be
excellent material choice for aerostructures. In structural design, plane strain fracture toughness is an
important property requirement. In our previous study, we found out a pre-extrusion heat-treatment iseffective in improving the fracture toughness of the Mg-Zn-Y-Al RS P/M alloys due to the formation of
micrometer-sized a-Mg DRX grains and block-shaped LPSO phase grains [7,8]. However, effect of othermanufacturing parameters and alloy composition on the fracture toughness and microstructure have notbeen clarified yet. In this study, therefore, we systematically investigated the effect of the heat-treatment
condition, extrusion condition, cooling rate during melt spinning, and alloy composition on the fracture
toughness and microstructure of the Mg-Zn-Y-Al RS P/M alloys. Furthermore, we tried to clarify the
toughening mechanisms of the Mg-Zn-Y-Al RS P/M alloys.
A master alloy ingot with a nominal composition of Mg96.75Zn0.85Y2.05, Mg96.95Zn0.85Y2.05Al0.15,
Mg96.75Zn0.85Y2.05Al0.35 (at.%), were prepared by high frequently induction melting. RS ribbons wereprepared by a single-roller melt spinning method with a circumferential speed of 10 m·s-1 and 42 m·s-1.
Then, the RS ribbons were compacted into copper billets and degassed at 523 K for 15 min. The RS
ribbon-compacted billets were heat-treated at 673 K and 738 K for 24 h. To consolidate the RS ribbons,
extrusions at an extrusion ratio of 10, temperatures of 608 K and 623 K, and ram speeds of 0.5 mm·s-1, 1
mm·s-1, 2 mm·s-1, 2.5 mm·s-1, and 3 mm·s-1 were performed. Mechanical properties were measured
through a tensile test and plane-strain fracture toughness test. Tensile tests were performed with an initialstrain rate of 5 x 10-4 s-1. Fracture toughness was tested following ASTM standards E399-12 with a test
speed of 0.55 MPa m1/2 s-1. Microstructure of the RS ribbon-consolidated specimen was investigated using
SEM, TEM, and HAADF-STEM. Crystal orientation analysis was performed by electron backscatter
diffraction (EBSD) technique.
The alloy composition and manufacturing process, such as pre-extrusion heat-treatment conditions andcooling rate during melt spinning were optimized for improving the fracture toughness of the LPSO-type
Mg-Zn-Y-Al RS P/M alloys. As a result, high-strength and high-toughness alloys with the yield stress of
400~460 MPa and plane-strain fracture toughness of 18~24 MPa m1/2 were developed. For the formationof the block-shaped LPSO phase, its dispersion and volume fraction are important in enhancing fracture
toughness of the Mg-Zn-Y-Al alloys, due to the frequent formation of microcracks and the promotion of
crack deflection. Moreover, the higher level of work hardenability induced by the fine DRX grains withlow dislocation density can improve their fracture toughness.
References[1] Y. Kawamura et al., Mater. Trans. 42 (2001) 1172-1176.
[2] Y. Kawamura et al., Magnes. Tech. 2005, ed. H. I. Kaplan (Warrendale, PA: TMS, 2005), 499-502.
[3] S. Yoshimoto et al., Mater. Trans. 47 (2006) 959-965.
[4] H. Okouchi et al., Mater. Sci. Forum 638-642 (2010) 1476-1481.
[5] S. Izumi et al., Corr. Sci. 51 (2009) 395-402.
[6] M.Yamasaki et al., App. Surf. Sci. 257 (2011) 8258-8267.
[7] S. Nishimoto et al., Mater. Sci. Eng. A 832 (2022) 142348.
[8] S. Nishimoto et al., Mater. Trans. 63 (2022) 1396-1405.

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Recrystallization Suppression and Kink Strengthening of MFS-type Mg-0.4Zn-1.0Y alloys
Masaru Hayashida1*, Shin-ichi Inoue2 and Yoshihito Kawamura2
Graduate Student, Graduate School of Science and Technology, Kumamoto University
2
Magnesium Research Center/Development of Materials Science, Kumamoto University
Email: 213d8871@st.kumamoto-u.ac.jp
1

Mg-Zn-Y alloys with a Long-Period Stacking Ordered (LPSO) structural phase have been reported toform kink bands by plastic forming, resulting in a significant increase in tensile yield strength maintaining
ductility [1-3]. The LPSO phase has a long-period stacking structure of soft a-Mg layers and hard clusterarranged layers (CAL) which is enriched with solute elements [4, 5]. Such a layered structure of soft andhard layers is called "mille-feuille structure (MFS)". Material strengthening in MFS-type Mg alloys byforming kink bands have been attracted attention [6, 7]. The MFS-type Mg-0.4Zn-1.0Y alloys used in thisstudy form an MFS microstructure with cluster-arranged nanoplates (CANaPs) by aging treatment after
solution treatment. The non-recrystallized region of the MFS-type Mg-0.4Zn-1.0Y alloys forms kinkbands by hot extrusion. These regions can improve the yield strength of the alloys by kink strengthening.
However, the effect of kink formation on mechanical properties has not been quantitatively evaluated. To
evaluate kink strengthening, other strengthening factors such as grain refinement strengthening and work
hardening must be eliminated. In this study, we established extrusion conditions to suppress dynamic
recrystallization (DRX) and annealing conditions to suppress static recrystallization (SRX). Moreover,
we investigated the microstructure and mechanical properties of the alloys to evaluate kink strengthening.
The nominal composition of the alloy used in this study was Mg-0.4Zn-1.0Y (at.%). RS ribbon was
prepared by a single-roller melt spinning method with a cooling rate of 1.4 x 105 K/s. RS ribbons werepressed into copper billets and degassed at 523 K for 15 min. To consolidate the RS ribbons, hot-pressing
was performed at 623 K. The hot-pressed alloy was solution heat-treated at 813 K for 72 h in Ar gas
atmosphere. After the solution heat-treatment, MFS material with precipitated CANaPs was prepared byaging at 623 K for 12 h. The MFS material was extruded at an extrusion temperature of 623 K, an extrusion
ratio of R5, and an extrusion ram speed of 1.5 mm/s in which DRX suppressed. After extrusion processing,annealing treatment was applied. Mechanical properties were evaluated using tensile tests with an initialstrain rate of 5.0 x 10-4 s-1. Microstructure was investigated by confocally optical microscope (OM), Xray diffraction (XRD), and scanning electron microscope (SEM). Crystal orientation analysis was also
performed by electron backscatter diffraction (EBSD) technique.
We revealed extrusion conditions that can suppress DRX. The extruded alloys without DRX
exhibited a tensile yield strength of 386 MPa and an elongation of 5.9%. On the other hand, theextruded alloys with DRX showed relatively lower tensile yield strength and higher elongation incomparison with the extruded alloys without DRX. Next, we revealed annealing conditions of the
extruded alloys to suppress SRX. The mechanical properties of the annealed alloys without SRX were
not changed by annealing. On the other hand, the tensile yield strength of the annealed alloys with SRX
decreased and their elongation increased with increasing the area fraction of SRXed region. Therefore,
the superior mechanical properties of the annealed alloys without DRX and SRX may be due to kinkstrengthening.
References[1] Y. Kawamura et al., Mater. Trans., 42 (2001) 1172-1176.
[2] Y. Kawamura et al., Magnes. Tech. 2005, ed. H. I. Kaplan (Warrendale, PA: TMS, 2005), 499-502.
[3] S. Yoshimoto et al., Mater. Trans., 47 (2006) 959-965.
[4] E. Abe et al., Philos. Mags. Lett. 91 (2011) 690-696.
[5] D. Egusa et al., Acta Mater. 60 (2012) 166-178.
[6] K. Hagihara et al., Intermetallics 18 (2010) 267-276.
[7] K. Hagihara et al., Mater. Sci. Forum 706-709 (2012) 1158-1163.

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Investigation of fracture toughness of extruded Mg-Zn-Y alloys with multimodal
microstructure
1

Taiga Yasuda1, Michiaki Yamasaki2, *, and Koji Hagihara3
Department of Materials Science, Graduate School of Science and Technology, Kumamoto University,
2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan
2
Magnesium Research Center, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 8608555, Japan
3
Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, Aichi 466-8555, Japan*
Email: yamasaki@gpo.kumamoto-u.ac.jp

Mg alloys are expected to be used as structural materials for transportation equipment because they are
one of the light structural materials. However, the application of this alloys as structural materials is
limited because the strength of them is low. Recently, Mg-Zn-Y alloys consisting of α-Mg matrix andlong-period stacking ordered (LPSO) structure phase were developed[1]. The alloys show excellent
mechanical properties after thermo-mechanical treatments such as extrusion and rolling. It is because themicrostructure of the extruded alloys are characterized by multimodal microstructure that consists of: fine
dynamically recrystallized (DRXed) α-Mg grains with a random crystallographic orientation, coarseworked α-Mg grains with strong fiber texture in which the <101" 0> of the grains are parallel to the
extrusion direction (ED), and LPSO phase grains also have a <101"0> fiber texture[2]. The DRXed α-Mggrains contribute to an improvement in ductility. The worked α-Mg grains and the LPSO phase grains act
as effective components for increasing the strength. In recent years, various studies have been conductedto commercialize the alloys. From a safety point of view, investigation of fracture toughness is important.
Nishimoto et al. reported the fracture toughness of the Mg-Zn-Y-Al RS ribbon-consolidated alloy[3].
However, there are few studies on the fracture toughness of alloys with multimodal microstructure.
Therefore, in this study, the fracture toughness was investigated by using several Mg-Zn-Y alloys withdifferent volume ratios of three regions in multimodal microstructure.
The materials were Mg97Zn1Y2 (at. %) alloys and Mg99.2Zn0.2Y0.6 alloys. The billets were extruded withan extrusion ratio of 10, extrusion temperatures of 573 K, 623 K, 673 K, 723 K, and an extrusion ram
speed of 0.9 mm s-1. The mechanical properties were evaluated by tensile tests and fracture toughness
tests. Tensile tests were carried out using an Instron testing machine at room temperature with an initialstrain rate of 5 x 10-4 s-1. The tensile axis was held parallel to the ED. The fracture toughness tests wereconducted by using 1/4 compact tension specimens as per the ASTM E399-20 standard. A testing speed
was 0.55 MPa m1/2 s-1. The loading directions were vertical to the ED (T-L specimen) and parallel to the
ED (L-T specimen). The microstructure was observed by optical microscopy and scanning electron
microscopy. The textures of the alloys were analyzed by an electron backscatter diffraction analysis.
Regardless of alloy compositions, volume fraction of DRXed grains increased with increasing
extrusion temperature. Conversely, volume fraction of worked grains decreases with increasing extrusion
temperature. Volume fraction of LPSO phase of M97Zn1Y2 and M99.2Zn0.2Y0.6 alloys were ~23% and~2%,
respectively. Ultimate tensile strength (UTS) and yield strength (YS) of the extruded two alloys decreased
with increasing extrusion temperature. UTS and YS of M97Zn1Y2 alloys were higher than those of
M99.2Zn0.2Y0.6 alloys. The fracture toughness of M97Zn1Y2 alloys also showed higher than that ofM99.2Zn0.2Y0.6 alloys at any extrusion temperature. In the T-L specimens of M97Zn1Y2 alloy, fracture
toughness increased with increasing extrusion temperature. It was observed that the worked grains
elongated along ED suppressed the deflection of cracks. On the other hand, fracture toughness of the LT specimens decreased with increasing extrusion temperature. This is due to texture orientation of theworked alpha-Mg and LPSO grains.
References[1] Y. Kawamura et al., Mater. Trans. 42 (2001) 1172-1176.
[2] M. Yamasaki et al., Acta Mater. 59 (2001) 3646-3658.
[3] S. Nishimoto et al., Mater. Sci. Eng. A 832 (2022) 142348.

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Mechanical properties and microstructure of dilute Mg-Y-Zn alloys prepared by
combination of low cooling rate solidification and extrusion techniques
Seitaro Ishizaki1, Michiaki Yamasaki1, *, Koji Hagihara2, and Yoshihito Kawamura3
1
Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
2
Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, Aichi 466-8555, Japan
3
MRC, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan*
Email: yamasaki@kumamoto-u.ac.jp
The wrought Mg-Y-Zn alloys containing long-period stacking ordered (LPSO) phase show excellent
mechanical properties[1]. Typical LPSO phase in Mg-Zn-RE alloys is found to have 18R and 14H
structures. These structures have chemical modulation around stacking fault, in which solute elements areenriched in four atomic layers (L12-type Zn6RE8 cluster-arranged layers: CALs) of closely packed planes
at six- and seven-period intervals, respectively. The unique crystallographic structure of LPSO phase
limits the activation of slip system to only the basal <a>slip at room temperature and suppresses
deformation twins. The strong constraint of the slip system activates kinks as a accommodative
deformation mechanism for plastic deformation[2]. It is known that introduction of deformation kink band
into the LPSO phase induces strength in extruded alloys. More recently, Hagihara et al. reported that a
deformation kink occurred not only in the LPSO single-phase crystal but also in dilute Mg99.2Y0.6Zn0.2
single crystal with aperiodic dispersion of the CALs [3, 4]. The kink-deformed Mg99.2Y0.6Zn0.2 single crystal
showed excellent mechanical properties. Therefore, in this study, we have attempted to develop highstrength polycrystalline dilute Mg-Y-Zn alloys with high density CALs by combination of low coolingrate solidification and extrusion techniques. The cooling rate and alloy compositional dependence onmechanical properties of the alloys has been investigated.
Mg99.2Y0.6Zn0.2 (at.%), Mg98.4Y1.2Zn0.4, and Mg97.6Y1.8Zn0.6 alloys were melted by high-frequency
induction heating and then solidified in a carbon crucible at cooling rates of 1.6 x 10-2, 3.4 x 10-2, 6.7 x
10-2, and 15 x 10-2, 10 Ks-1. These alloys were gravity-cast at the cooling rate of 10 Ks-1, and then heattreated (solution-treated at 793 K for 5 h, and then aged at 573 K for 5 h). The extrusion was performedat an extrusion temperature of 573 K and an extrusion ratio of R10. Mechanical properties were evaluatedby Instron-type tensile test. Microstructure was observed by OM, SEM/EBSD, and TEM.
It was confirmed that the as-solidified Mg99.2Y0.6Zn0.2 alloys that were produced via furnace coolingpossessed large CALs-dispersed regions. The area fraction of the CALs-dispersed region tends to increase
with decreasing cooling rate. In other words, the two-region structure that consists of the CALs-dispersed
region and solute-lean alpha-Mg matrix region could be formed by cooling rate control technique.
The area fraction of the CALs-dispersed region in the solidified alloys affects the multimodal
microstructure evolution and mechanical properties of the extruded ones. The area fraction of the worked
grain region in the extruded alloys and the kink dispersion in the worked grain region increased withincreasing the CALs-dispersed region. Developing the kink-deformed worked grain region strengthen thealloy. It was also revealed that decrease in the density of CALs in the CALs-dispersed region promoted
dynamic recrystallization during extrusion. Increase in the dynamic recrystallized grain region improve
ductility of the alloy. In addition to the area fraction of the CALs-dispersed region, the density of CALs
in the CALs-dispersed region in as-solidified alloys definitely affects multimodal microstructure
evolution.
References[1] Y. Kawamura et al.: Mater. Trans., 48 (2007) 2986-2992.
[2] K. Hagihara et al.: Acta Mater, 163 (2019) 226-239.
[3] K. Hagihara et al.: Acta Mater, 209 (2021) 116797.
[4] K. Hagihara et al.: Mater. Res. Lett., 9 (2021) 467-474.

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The Effect of Hot Rolling on Kink Formation in the MFS-type Mg-0.4Zn-1.0Y Alloywith a-Mg Single Phase.
Ayami Yoshida1*, Shin-ichi Inoue2, and Yoshihito Kawamura2
1
Graduate Student, Graduate School of Science and Technology, Kumamoto University
2
Magnesium Research Center/Department of Material Science, Kumamoto University*
Email: 220d8883@st.kumamoto-u.ac.jp
Magnesium alloys containing a long period stacking ordered (LPSO) phase have attracted a great dealof attention because of its excellent mechanical properties [1]. The property enhancement was mainly
caused by kink deformation and strengthening in LPSO phase. The LPSO phase consists of hard- andsoft-layers, in which the hard-layer is a cluster arranged layers (CAL) enriched with solute elements andthe soft-layer is the α-Mg layers. Such layered structure is called “mille-feuille structure (MFS)”. Recently,
it was found that kink deformation occurs not only in the LPSO structure, but also in a non-periodic MFS
with cluster arranged nanoplates (CANaPs).
In the previous studies, the non-recrystallized region of MFS-type Mg-0.4Zn-1.0Y (at%) alloys with aMg single phase form kink bands by hot extrusion. This region can improve the yield strength of thealloys by kink strengthening. However, kink strengthening should be investigated under conditions ofsuppressed recrystallisation. Rolling process is an effective and more quantitative method ofinvestigating kink deformation while suppressing recrystallisation, as it can introduce low amounts ofstrain multiple times. Therefore, this study is aimed to study the effect of deformation strain on thekink formation and mechanical property of the MFS-type Mg-0.4Zn-1.0Y alloy.
The master ingot with a nominal composition of Mg-0.4Zn-1.0Y (at%) was prepared by high frequency
induction melting and casting. Rapidly solidified (RS) melt-spun ribbons were compacted into copper
billet and first degassed at 523K for 15 min. The billets were then hot pressed at 623K for 10 min. After
hot pressing, the bulk alloys were solution treated at 813K for 72h and then aged at 623K for 12h. After
aging treatment, hot rolling was carried out at 573K, at a peripheral speed of 8.0 x 10-3 m/s, and a thickness
reduction ratio of 5% per pass. The final total deformation strains were set at 0.5 and 1.0. Tensile test
were conducted at room temperature with an initial strain rate of 5 x 10-4 /s. Microstructure wascharacterized by using SEM and SEM/EBSD.
The tensile yield strength of the hot-rolled alloy with total strain of 1.0 was two times as high as asaged alloy. Figure 1 shows the SEM microstructures of as-aged and as-rolled specimens. Many chevronshaped kink bands were observed on both the RD (rolling direction) and the TD (transverse direction)
samples, Fig. (c) and (d). But only few kink bands were observed on the ND (normal direction) sample,
Fig. (b). The dispersion of the kink bands and their bending angle observed on the RD and TD planes
increase with increasing total deformation strain. The result shows that the kink bands form and kinkstrengthening takes place in the hot-rolled MFS-type Mg-0.4Zn-1.0Y alloy.

Fig. 1 SEM microstructures of MFS-type Mg-0.4Zn-1.0Y alloys: (a) as-aged, (b) S𝜀̅ = 1.0 for ND, (c) S𝜀̅ = 1.0 for RD,(d) S𝜀̅ = 1.0 for TD.

References[1] Y. Kawamura, K. Hayashi, A. Inoue, and T. Masumoto, Mater. Trans. 42 (2001) 1172-1176.

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Work-hardening Behavior of Mg-Y-Zn Alloy with Long-periodic Stacking Ordered Phasein High-pressure Torsion Process
Hiromu Ohkoshi 1*, Yoshikazu Todaka 1, Nozomu Adachi 1, Itsuki Fukuoka 1, Mizuki Kouno 1,
Nobuhide Kaneda 1, Hidetoshi Somekawa 2, Daisuke Ando 3, and Motohiro Yuasa 4
1
Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi 441-8580, Japan
2
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
3
Tohoku University, 6-6-11 Aoba, Aramaki, Aoba-ku, Miyagi 980-8579, Japan
4
Doshisha University, 1-3 Miyakodani, Tatara, Kyotanabe 610-0394, Japan*
Email: okoshi.hiromu.rd@tut.jp

Vickers hardness, HV / GPa

Our previous study has showed the effect of wrought-processing on kink boundary formation andmechanical properties using the Mg - 9at.%Y - 6at.%Zn alloy consisting of the long-periodic stacking
ordered (LPSO) single phase (Mg-Y-Zn alloy). [1] Hardness closely related to the magnitude ofequivalent plastic strain introduced by the wrought-processing. Among the various wrought-processes,
the Mg-Y-Zn alloy after high-pressure torsion (HPT) processing, in which torsion is applied under highcompressive stress, exhibited excellent work-hardening behavior. The aim of this study is to investigate
the effects of initial microstructure in the Mg-Y-Zn alloy on kink boundary formation and work-hardening
behavior in the HPT process. The effect of processing
2.2
temperature was also investigated.
● DS_0 , N = 1/4
2.0
The Mg-Y-Zn alloys produced by casting (Cast) and◯ DS_90 , N = 1/4
1.8
directional solidification (DS) were deformed by HPT
r = 1mm(r : distance from HPT disk center)
processing. Figure 1 shows the Vickers hardness of the Mg1.6
Y-Zn alloys after HPT processing. The DS_0° specimen
1.4
which was cut perpendicular to the <1 1 -2 0> growth
1.2
direction showed higher value after compressive deformation
DS_0 , N = 0: HV 1.04 GPa
1.0(Number of turns N = 0) in the HPT process than the DS_90°
DS_90 , N = 0: HV 0.90 GPa
specimen cut parallel to the growth direction. This reason
0.8
is that the formation of the kink boundaries facilitated
0.6
0
0.5
1.0
1.5
2.0
2.5
3.0
through compressive deformation because the (0 0 0 1) basal
Hencky equivalent strain, eeq
planes in the DS_0° specimen were parallel to thecompression axis.
However, the subsequent torsional Fig.1 Vickers hardness in DS
deformation resulted in higher work-hardening in the DS_90° specimens after HPT process.
specimen. The Cast specimen showed the similar result to
the DS_90° specimen. In the DS_90° and Cast specimens,
numerous finer kink bands were formed compared to theDS_0° specimen, as shown in Fig.2, indicating that theformation of such microstructures results in the higher workhardening. It was also found that more effective workhardening (kink band formation and microstructurerefinement) could be achieved by controlling the processing
temperature in the HPT process to accelerate plastic
deformation.
Reference[1] H. Somekawa, Y. Todaka, D. Ando, M. Yuasa, Materials
Letters, 304 (2021) 130653.
Acknowledgement
This work was supported by the JSPS Scientific Research on
Innovative Areas “MFS Materials Science in No.
18H05477”.

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Fig.2 Microstructure in DS specimens
after HPT process (N = 1/4, r = 1mm).

Texture evolution and mechanical properties of Mg-2Y-1Zn alloy via vortex extrusion
Takumi Tsuji1*, Daisuke Ando1, Takenori Tanno2, Motohiro Yuasa3,
Hidetoshi Somekawa4, and Yuji Sutou1
1

Department of Materials Science, Graduate School of Engineering, Tohoku University,
6-6-11 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579,
2
Research Institute of Electrical Communication, Tohoku University,
2-1-1 Katahira, Aoba-ku, Sendai, Miyagi, Japan 980-8577
3
Department of Mechanical Engineering and Science, Faculty of Science and Engineering,
Doshisha University, 1-3 Miyakodani, Tatara, Kyotanabe, 610-0394, Japan
4
National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, Ibaraki 305-0047, Japan
5
Japan Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku
Sendai, Miyagi 980-8577, Japan Research Center for Structural Materials,*Email: takumi.tsuji.p1@dc.tohoku.ac.jp
LPSO-type magnesium alloys have a two-phase alloy consisting of an α-Mg phase and an LPSO phase;in Mg-2Y-1Zn alloys, the volume fraction of the LPSO phase is about 25%. This alloy exhibits ordinary
mechanical properties in the cast state, but it is known that the mechanical properties can be significantly
enhanced by warm extrusion. The extrusion ratio required for this strengthening is 3-10. The equivalent
plastic strain is about 1.0-2.3. This work ratio is relatively smaller than that required to fabricate aconventional wrought Mg alloy. If the extrusion ratio is further increased, the alloy tended to soften due
to dynamic recrystallization caused by processing heat. On the other hand, some researchers have reported
that in Mg-9Y-6Zn alloys exhibiting a single phase of LPSO, the more equivalent strain applied, the more
kink-strengthened this alloy turns out to be. The reason is thought to be that the kink deformation of the
LPSO phase without recrystallization increases the plastic deformation resistance of the basal slip. From
another perspective, some other researchers have reported that in Mg-Gd-Y-Zn alloys with LPSO phases,
using the severe plastic deformation method results in strengthening of the alloy by refining the
microstructure. In this study, we focus on vortex extrusion, in which a large shear strain can be added to
the normal extrusion process by carving a groove in the die that rotates the work piece in warm extrusion,
to investigate the microstructural evolution of the Mg-2Y-1Zn alloy and its mechanical properties when
the amount of strain applied, in this case the material rotation angle, is changed. The results showed that
the Vickers hardness increased as the rotation angle was increased. Observation of the microstructure
showed that the kink deformation changed from a ridge-type kink, in which the LPSO phase folds in a
zigzag pattern, to an ortho-type kink, in which the LPSO phase curves with a gradual change in angle. In
the day's presentation, we would also show the results of XRD and SEM/EBSD investigating the texture
evolution and the percentage of dynamic recrystallization.

Fig. 1. Vickers Hardness with or without vortex Fig.2 Microstructure change after vortex extrusion-76-

Numerical Investigation of the Microstructural Features Favoring Kink Band in Layered
α/β Ti-9Cr Alloy
Junyu Zhu (D3)1, Fabien Briffod1, Takayuki Shiraiwa1, Satoshi Emura2, Manabu Enoki1
1
The university of Tokyo, 7-3-1 Hongō, Bunkyo City, Tokyo 113-8654, Japan
2
National Institute for Material Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
Email: junyuzhu@rme.mm.t.u-tokyo.ac.jp
Deformation kink bands were found in a layered α/β Ti-9Cr alloy after uniaxial compression tests. The
metastable Ti-9Cr alloy was developed with a controlled thermomechanical process to decrease thedislocation mean free path in the β phase and obstruct the softer deformation mechanisms [1]. In thisstudy, the effect of alternative stacking α/β layers on the kink deformation mechanism was simulated with
Crystal Plasticity Finite Element Method (CPFEM).
The mechanical properties of the Ti-9Cr alloys were investigated with uniaxial compression tests. The
microstructures of the deformed surface were then characterized by SEM, TEM observation, and EBSDEDS measurements to identify the crystal orientation and operative deformation mechanism.
Nanoindentation tests were carried out on the undeformed specimen. The CP parameters were calibrated
according to the response of the nanoindentation tests. Phenomenological crystal plasticity models withdifferent sets of dimensions and tilt angles were developed. 25% of plastic strain was applied to themodels with corresponding boundary conditions to simulate the mechanical response of the layered
structure in the CPFEM software Abaqus. By inspecting the favorable microstructure for the deformation
kinking to take place, the mechanism of kink band formation was evaluated.

References[1] S. Emura and X. Ji, Mater. Trans. 61 (2020) 856-861.

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Deformation mechanism of LPSO-type Mg alloy after kink deformation
Kosuke Gonome1*, Daisuke Egusa1, and Eiji Abe1, 2
The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, JAPAN
2
National Institute of Materials Science, 1-2-1, Sengen, Tsukuba-shi, Ibaraki, 305-0047, JAPAN*
Email: gonome@stem.t.u-tokyo.ac.jp
1

Mg alloys containing long period stacking/order (LPSO) phase appear high strength by adapting hightemperature processing. The strengthening of LPSO-type Mg alloys is believed to derive from kinkdeformation which has been experimentally demonstrated [1]; however, details of kink deformation
mechanisms have not yet been elucidated. The main deformation modes in the LPSO phase are limited tobasal slips and kink deformations, due to the high anisotropy of the LPSO structure. Kink deformation isthought to dominate their yielding, especially in situations where basal slip is suppressed, but it is notclear what deformation mechanisms are active when further additional deformation is applied after kinkdeformation. In this study, we observed deformation microstructures of LPSO-type Mg alloys compressedat room temperature to beyond the yielding to clarify the deformation mechanisms that develop in thekink deformed microstructure.
We prepared directionally solidified Mg85Zn6Y9 (at.%) alloy that is compressed at room temperature
up to the nominal strain of 10 %. Microstructures were investigated with scanning electron microscopy(SEM), transmission electron microscopy (TEM) and aberration-corrected scanning transmission electron
microscopy (STEM) operating at 200kV.
Fig. 1 shows a TEM bright field image obtained from the compressed Mg85Zn6Y9 alloy. Kinkboundaries (KBs) were often observed, as indicated by the white arrowheads, and rotation angles at theKBs were generally greater than 10 degrees. Focusing on the near-KB, several boundaries extended fromthe KB, which are inclined from the KB. According to Rank-1 theory [2], boundaries inclined to the KB
do not necessarily satisfy the continuity of deformation, suggesting that the boundaries introduced by adeformation mechanism different from kink deformation. Fig. 2 shows a LAADF-STEM image, strongly
enhance strain contrast, obtained around the KB. The boundaries (denoted as SB: secondary boundary,hereafter) can be confirmed as bright contrasts which were aligned with an average interval of about 200
nm and terminated within the grain. Angles between KB and SB are constant at almost 58 ± 1.5 degrees,
indicating that SB exhibits features similar to shear bands. If the shear bands are terminated within thegrain, additional deformation is necessary to compensate for the deformation discontinuities. Fig. 3 (a)shows an atomic resolution STEM image around the intersection between KB and SB. At the SB, thebasal plane is rotated by a few degrees, suggesting that crystal rotation occurred to resolve the deformation
discontinuity. Fig. 3 (b, c) shows a schematic illustration of the SB introduction on KB. When the KB
moves due to additional deformation, there is a volume discontinuity between the left and right sides ofthe boundary. Introductions of SB will compensate the discontinuity, which can be represented by adisclination dipole. In the presentation, we will discuss details on structural features of SB and its role on
deformation after yielding of the alloy.

Fig.1 Bright-field TEM
image of a LPSO grainin the Mg85Zn6Y9 alloy_

Fig. 2 [1100] projected LAADF-STEM Fig. 3 Atomic resolution STEM
image around the intersection
image of a KB and SBs
between KB and SB

References[1] K. Hagihara et al., Acta Materialia, 163 (2019) 226-239.
[2] T. Inamura, Acta Materialia, 173 (2019) 270-280.

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Deformed microstructure in LPSO-type magnesium alloys exhibiting PLC effectNaoki Amemiya1*, Daisuke Egusa1, Tomotaka Miyazawa2, Toshiyuki Fujii2, Eiji Abe1,3
1
The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, JAPAN2
Tokyo Institute of Technology,2-12-1, Ookayama, Meguro-ku, Tokyo,152-8550, JAPAN3
National Institute for Materials Science, 1-2-1 Sengen ,Tsukuba-shi, Ibaraki, 305-0047, JAPAN,*Email:amemiya@stem.t.u-tokyo.ac.jp
Magnesium alloys containing a few atomic percent of Zn/RE (RE denotes rare earth) form a phasewith a unique structure called long period stacking/order (LPSO) structure. In this structure, stacking
faults are periodically introduced into α-Mg which has an hcp structure, and solute is concentrated in the
fcc structure formed by the stacking faults1). The superior strength of this alloy is believed to be due tothe kink boundary formed in the LPSO phase. Hagihara et al2). evaluated kink strengthening andreported that the kink boundary acts as a resistance to basal slip. He also reported that kinkstrengthening can be expected to provide further strengthening in addition to the conventional
strengthening mechanism. Recently, the Portevin-Le Chatelier (PLC) effect has been found to occur inroom temperature deformation of LPSO phases. The PLC effect is understood as a phenomenon causedby the interaction between dislocations and solute atoms, which results in negative strain rate sensitivity
3). Although the PLC effect is generally observed in high-temperature processing, in the case of the
LPSO phase, it is observed in room-temperature compression. The purpose of this study is to find themicrostructural features responsible for the PLC effect in deformed Mg-Zn-Y alloys.
Directional solidified Mg85Zn6Y9 (at. %) alloys were compressed in the direction parallel to thesolidification direction at room temperature. To evaluate strain rate sensitivity (m-value), the specimen
was compressed at two different strain rates (1.67 × 10-3/s, 1.67 × 10-4/s) until the m-value became
negative and the PLC effect was clearly observed (nominal strain 15%). After compression, thespecimens were mechanically polished, then ion-milled into thin foils for STEM observation.
Fig. 1 (a) shows a HAADF-STEM image of the kink boundary. The image intensity increases on thekink boundary indicated by arrows, suggesting that solute atoms segregate at the boundary even though
the specimen was deformed at room temperature. The wavy shape of the kink boundary and discrepancy
in the stacking of the LPSO phases on either side of the boundary suggests that the kink boundary
moved with further deformation after it was formed. In addition, solute segregation can be observed in
the rectangular region near the kink boundary in Fig.1(a). Fig. 1 (b) shows a magnified HAADF-STEM
image of the rectangular region in Fig. 1 (a). Burgers circuit analysis _in Fig. 1 (b) indicates that there isa defect corresponding to the Frank partial dislocation (b = 1/6[2023] in hcp) in the solute segregatedregion. Fig. 1 (c) shows the intensity profiles obtained in regions ① and ②in Fig. 1 (b). Based on theintensity profiles, we found that the existence of the <a+c> dislocation changed the stacking structurefrom intrinsic-II type stacking
fault to extrinsic type stacking
fault.
The above results suggestthat the migration of kinkboundary with solute segregationand the formation of defects
including <c> contribute to the
PLC effect observed in this alloy.
Details of microstructure will be
discussed in the presentations.
References[1] D. Egusa, E. Abe, Acta Mater.,
60 (2012), 166-178[2] K. Hagihara et al., Acta Mater., Fig. 1 (a)HAADF-STEM image of kink boundary in Mg85Zn6Y9
163 (2019), 226-239
alloy, (b)HAADF-STEM image around the <a+c> dislocation in[3] F. Wang et al., Acta Mater., 165 (a), (c) intensity profile of the area ①,② in (b)(2019), 471-485-79-

Dislocation analysis of solute-enriched stacking faults
in kink boundaries in Mg97Zn1Y2 alloys
Yifang Zhao1*, Hongye Gao1, Zimeng Guo1, Daisuke Egusa2, Eiji Abe2, and Satoshi Hata1
Kyushu University of Kyushu, 6-1 Kasugakoen, Kasuga-shi, Fukuoka, 816-8580, JAPAN2
The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, JAPAN*Email: zhao.yifang.918@s.kyushu-u.ac.jp

1

Mg-Zn-RE (rare earth elements) alloys have received great attention in the field of light metal researchbecause of their superior mechanical properties. This fact is due to a unique alloy strengthening of kinkdeformation promoted by long-period stacking order (LPSO) structure. The microstructure formed bykink deformation is typically characterized as kink boundaries (KBs) accompanied by crystal rotation. In
LPSO structures, KBs are often manifested as micrometer-scale flat boundaries accompanied bygeometrically necessary (GN) dislocations arrays. These flat boundaries are essentially enriched with thesolute Zn/RE atoms (solute-enriched stacking faults, hereafter referred to as SESFs) [1]. Recent reports
indicate that SESFs in the α-Mg matrix can also cause kink deformation and promote kink strengthening
in some Mg-Zn-RE alloys [2]. In this study, we observed microstructures around KBs to characterize theconfiguration of SESFs and dislocations.
The KBs in the annealed Mg97Zn1Y2 specimen were observed using a scanning transmission electron
microscope (STEM), Titan Cubed G2, operated at an acceleration voltage of 300 kV under a parallelbeam STEM mode with a convergence semi-angle of 1.2 mrad. The specimen was set in a two-beamexcitation condition for g = 0006 during specimen tilt. The bright-field (BF), dark-field (DF) and highangle annular dark-field (HAADF) images were obtained by detecting the direct beam (0 ~ 5 mrad),diffracted beams in the range of 7–49 mrad, and diffracted beams in 52–200 mrad, respectively.
Figure 1 shows a BF-STEM image obtained under the two-beam condition, 𝑔 = 0006. In this condition,c’-dislocations, which have c<000l> components in their Burgers vectors, are visible. By measuring therotation angles at KBs from the solute Zn/Y atom enrichment layers arranged along Mg(0001), indicatedby white dotted lines, it was noted that the crystal was rotated about 4.2° and 1.4°at KB1 and KB2,
indicated by black dotted lines, respectively. The KB is shown here as arrays of stacking-fault layers withshort linear dark contrast that are composed of the SESFs and GN dislocations. Both KB1 and KB2 aresegmented at inflection points to form step shapes, which are common features in annealed specimens [2].
Within the KBs, the c’-dislocations only appear at the position of segmentation indicated by black arrows.
This can be explained that the crystal rotation becomes discontinuous at the terminated edges of thesegmented KBs, and this discontinuity is compensated by the introduction of an array of non-basal
dislocations to avoid the appearance of micro-voids [2]. Outside the KBs, the c’-dislocations appears
inside the linear solute Zn/Y atom enrichment area indicated by white arrows. This can be explained thatthe solute-atom enrichment area can bec’-dislocations
separated into the nanosized segments by c’(a)inside KB
dislocations, and these nanosized segments canform the tilt boundary to significantly reduce
KB1c’-dislocations
KB2
the boundary energy [3]. Based on theoutside KB
observation results described above, theformation process of the microstructure at theKBs will be discussed using a dislocationdisclination model.
[0002]

References[1] M. Egami et al., Materials & Design 188(2020) 108452.
[2] D. Egusa et al., Materials
Characterization 177 (2021) 111153.
[3] X. Shao et al., Materialia 6 (2019) 100287.

100 nmbasal plane[0110][2110]

Fig. 1. BF-STEM observation of SESFs and c'dislocations in KBs in Mg97Zn1Y2 specimen.

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Deformation anisotropy in hcp-Mg structure based on generalized stacking fault energy
Yuto Ito1*, Daisuke Egusa1, Masatake Yamaguchi1,2, and Eiji Abe1, 3
The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, JAPAN
2
Japan Atomic Energy Agency , 2-4 ,Shirakata, Nakagun Tokaimura, Ibaraki, 319-1195, JAPAN3
National Institute for Materials Science, 1-2-1 Sengen ,Tsukuba-shi, Ibaraki, 305-0047, JAPAN*Email: ito@stem.t.u-tokyo.ac.jp
1

Mg alloys containing long-period stacking/order structure (LPSO) phases exhibit high strength that isbelieved to derive from kink deformation due to the high structural anisotropy of the LPSO phase. Kink
deformation is represented by the collective motion of dislocations in limited slip systems, which forms
sharp kink boundaries with crystal rotation. However, detailed mechanisms of kink deformation and theirstrengthening mechanism are still unclear. In this study, we have investigated an anisotropy of dislocation
motion under uniaxial compressive stress on the hcp-Mg structure, based on the generalized stacking fault
energy (GSFE) calculated by first-principles calculations to deepen our understanding on the kinkdeformation mechanism.
For calculations of GSFE, we set a superlattice of the hcp-Mg structure as a model structure. Structural
optimizations were performed by the VASP code. Fig. 1(a) shows the [0001] projection of the model cellwith a dimension of 1×1×3 to the hcp-Mg. The maximum restoring stress 𝜏𝑚𝑎𝑥 was calculated along thepath with the minimum GSFE gradient, and the Peierls stress 𝜎𝑝 was evaluated using the Joos andDuesbery equation [1]. We also calculated GSFE and Peierls stresses with the model structures under
uniaxial compression of 5% along the [112̅0] and [11̅00] directions, respectively.
Fig. 1(b) shows a calculated GSFE surface with the optimized hcp-Mg cell. The path with the smallest
GSFE gradient is depicted by the arrows which correspond to the partial dislocations of the basal slip in
the hcp-Mg. Fig. 1 (c) shows a profile of GSFE along the path. The highest gradient of GSFE (𝜏𝑚𝑎𝑥 ) was
1.6 GPa that represents the Peierls stress of 𝜎𝑝 =3.6 MPa. The corresponding GSFE curves with uniaxial
compressions are also plotted in Fig. 1 (c). When the model compressed along the [11̅00] direction, thefirst peak of GSFE apparently decreased, resulting in a decrease of the Peierls stress of corresponding
partial dislocations to 𝜎𝑝11̅00=0.023 MPa, that is about 1% of the one in the original hcp-Mg. On the other
hand, the Peierls stress in the [101̅0] direction increased to 𝜎𝑝101̅0=11 MPa, indicating the dislocation
motion show high anisotropy by the compressive stress. In the case of compression along the [112̅0]
direction resulted in 𝜎𝑝11̅00=4.2 MPa and 𝜎𝑝101̅0 =3.2 MPa. The above results indicate that compressive
stress may provide anisotropy in the equivalent slip system, leading to activating different deformation
modes.

Fig. 1 (a) [0001] projection of Slab cell. (b) GSFE surface for each atomic displacement.
(c) GSFE curves of the models with each stress state.
Reference[1] B. Joos, M. S. Duesbery, PRL., 78(1997) 266-269.

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Elastic energy of disclination multipole formed at intersection ofkink band and shear band
Ryutaro Matsumura1*、Yuri Ueda1、Yuri Shinohara2、Tomonari Inamura2
1
Graduate Student, Department of Material Science and Engineering,Tokyo Institute of Technology, 4259 Nagatsutacho, Midori-ku, Yokohama 226-8503, Japan
2
IIR, Tokyo Institute of Technology, 4259 Nagatsutacho, Midori-ku, Yokohama 226-8503, Japan*Email: matsumura.r.aa@m.titech.ac.jp

In order to construct a theory of kink strengthening found in LPSO-Mg alloys [1], we have
performed kinematic analysis of kink band, ridge kink, and ortho kink sheared by basal slip
using the rank-1 connection which is a condition for the continuity of deformation. We haveshown that disclination multipole is formed at the intersection of shear band and kink andthey should act as energy barrier for deformation[2,3]. In this study, we investigate theeffect of disclination multipole formed in these three types of kinks on the deformation
behavior in terms of elastic energy of the disclination multipole (Em).
We define a shear band as a region of uniform shear deformation parallel to the basal
plane with a finite thickness, d. Kink band is characterized by the basal shear and rigid
body rotation as described by the model by Inamura[4]. The sign of the shear direction isimportant to consider ridge and ortho kinks. Connecting two kink bands which were formedby the basal slips with opposite sign form ridge kink. Ortho kink is defined as aggregate ofkink bands with the same sign of the basal shear. When the three types of kinks, namely
kink band, ridge kink and ortho kink, are sheared by the shear band with keeping thecontinuity of deformation, additional rigid body rotation is required at the intersection of
the kink and the shear band. This rotation generates disclination multipole at theintersection[2]. The configuration and the strength of disclination multipole were obtainedby analyzing Rank-1 connection. Em was evaluated using the elastic energy of disclination
multipole formula derived by Romanov et al[5].
Figure 1 and 2 schematically show disclination multipole formed in sheared kink bandand sheared ridge kink, respectively. In these figures, the magnitude of shear to form kinkband is s1=0.3 in Fig.1, s2=0.3 and s3=－0.3 for ridge kink in Fig.2 with the thickness of theshear band d = 10-6m, kink width l= 10-5m, the magnitude of shear in the shear band sm =0.002. Figure 3 shows Em of disclination multipole with the integral radius R from the centerof the multipole as a variable. In this example, we found Em for ridge kink is higher thanthat of kink band. Em is evaluated for three types of kinks and its effects on the deformation
behavior will be discussed.

Fig.1 Sheared kink band

Fig.2 Sheared ridge kinkFig.3 Em (disclination multipole)

References[1]K.Hagihara, et. al. Materials Science & Engineering A 763 (2019) 138163[2]R.Matsumura, et. al. Fall Meeting, The Japan Institute of Metals and Material(2021)[3]R.Matsumura, et. al. Spring Meeting, The Japan Institute of Metals and Material (2022)[4]T.Inamura, Acta Materialia 173 (2019) 270-280[5]A.E.Romanov, et. al. Letters on Materials 8 (2018) 384-400
Acknowledgment: This work was supported by JSPS KAKENHI for Scientific Research on Innovative Areas MFS Materials
Science (Grant Number JP18H05481), and IIR Research Fellow program.

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Stable Shape of Curved Ridge-Kink Consisting of a Sequence of Fine Kink-bands
1

Xueyu Zhang1*, Ryutaro Matsumura1, Yuri Shinohara 2, and Tomonari Inamura2
Graduate Student, Department of Materials Science and Engineering, Tokyo Institute of Technology,
4259 Nagatsutacho, Midori-ku, Yokohama 226-8503, JAPAN2
IIR, Tokyo Institute of Technology, 4259 Nagatsutacho, Midori-ku, Yokohama 226-8503, JAPAN*
Email: zhang.x.be@m.titech.ac.jp

A geometric model that can quantitatively describe kink deformation is required to elucidate themechanism of "kink strengthening" which has been discovered in LPSO-Mg alloys. Based on the rank-1
connection, which is the condition for continuity of deformation, Inamura [1] proposed a geometric modelof kink deformation that is consistent with experimental results and proved that the lattice defects called
disclinations inevitably exist in connecting kink-bands. Such disclinations should have significant impacts
on the formation of kink-microstructure and the mechanical properties of the material. However,Inamura's model cannot quantitatively describe various kink structures observed in experiments [2],especially kinks with curved boundaries. In this study, we formulate the geometry of a curved kinkmicrostructure by extending Inamura's model and clarify the stable shape of a curved kink by elastic
energy minimization.
We modeled a curved kink by introducing a sequence of ortho-kinks parametrized by a vector
s=(s1,…,is,…son) (called "shear vector", hereafter) into a ridge kink with uniform shear s0, where isrepresents the uniform shear of the i-th internal ortho kink. And the inequality s0>s1>s2>…>son>0 is set toexpress the experimentally observed feature of ridge-kink such that a curved kink boundary is convex
towards the exterior of the kink. For a given shear sequence s, we can analytically obtain thecorresponding shape of the kink and the accompanying disclinations using Inamura's model. The elastic
energy, Etot, due to the accompanying disclinations is computed using Romanov's model in the frameworkof linear elasticity [3]. We define the elastic-energy parameterized by the shear vector s as Etot= E(s).
Then, according to the principle of minimum potential energy, the stable shape of the kink, ŝ, is obtainedby the minimization of E(s) as ŝ=argmin E(s).
As a result, it was found that the minimum value of E(s), Ê, decreases rapidly and then graduallyconverges to a certain constant as the number of the internal ortho-kinks, n, increases. In other words,
from an elastic point of view, the curved kink with more internal ortho-kinks is preferred in the material.
It is, therefore, deduced that the curved kink observed experimentally is formed as the relaxation of thedisclinations. We also analyzed the geometry of the curved kink when n→∞, and it was in good
agreement with the morphology of the curved kink in experiments, as shown in Fig. 1 (b).

Fig. 1. (a) The plot of the number of the internal ortho kinks (n) and the minimum elastic energy Ê.
(b) Morphology of the curved kink (n→∞) with a microscopy image (bottom).
References[1] T. Inamura, Acta Mater. 173 (2019) 270-280.
[2] D. Egusa, et al. Mater. Trans. 54 (2013) 698-702.
[3] A. E. Romanov, Prog. Mater. Sci. 54 (2009) 740-769.

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Experimental Verifications of Kink-Band Strengthening in Long-Period Stacking
Ordered Mg–Zn–Y Alloy
Tsubasa Tokuzumi1*, Aoi Fukushima1, Masatoshi Mitsuhara2, Shigeto Yamasaki3, Tomonari Inamura4,
Toshiyuki Fujii5, and Hideharu Nakashima2
1
Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1, Kasuga-koen,
Kasuga, 816-8580, JAPAN
2
Department of Advanced Materials Science and Engineering, Kyushu University, 6-1, Kasuga-koen,
Kasuga, 816-8580, JAPAN
3
Department of Materials, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka, 819-0395, JAPAN
4
Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute ofTechnology, 4259, Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, JAPAN5
School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1, Ookayama,
Meguro-ku, Tokyo, 152-8552, JAPAN*Email: tokuzumi.tsubasa.092@s.kyushu-u.ac.jp
Mg–Zn–Y alloys that contain a Mg-based long-period stacking ordered (LPSO) phase exhibit
excellent mechanical properties because of the kink bands formed by plastic deformation. These
properties have attracted significant attention as the kink-band strengthening [1]. Herein, we conducted
deformation tests and electron microscopy to investigate the kink-band strengthening mechanism.
The master ingot was a LPSO single-phase directionally solidified Mg85Zn6Y9 alloy. In the alloy, thec-axis and <112#0> directions of the LPSO phase were respectively almost perpendicular and parallel tothe growth direction of the DS specimens. The plate-like specimen was approximately 3 mm × 4 mm ×
1 mm (W × L × T), with the longer side of the specimen parallel to the direction of growth, that is, the 0°orientation. Kink bands were formed on the specimens by manual compression tests using a vice atroom temperature; the loading axis was parallel to the 0° orientation. The surface relief of the kinkbands was flattened by mirror polishing using a diamond suspension. Then, we performed double
deformation tests with a second loading in the 45° orientation after a first compression in the 0°orientation. Simple compression (i.e., double compression) or tensile via bending was applied to theloading in the 45° orientation. To prove the existence of disclinations around the kink bands, themagnitude of the Frank vector ω was estimated using high-angular-resolution electron backscatter
diffraction (EBSD) measurements by scanning electron microscopy (SEM). The SEM image
observations were conducted. These SEM images were used for digital image correlation (DIC)
analyses to quantify the amount of plastic strain.
An EBSD analysis was performed to detect misorientations between the matrices across the kinkbands. The existence of disinclinations was supported by the misorientations, that are the Frank vectorsof the disclinations around the kink, and closely matched estimation results from the geometric analysis[2]. Moreover, the Frank vector increased by shear deformation (second loading in the 45° orientation)of the kink bands. The introduction of new disclinations around the kink may have resulted from shear
deformation. The SEM observation demonstrated that the kink clearly obstructed basal <a> slips. Thisis definitive experimental evidence that kink bands behave as an obstacle to subsequent deformations,that is, we confirmed the kink-band strengthening phenomenon. When the shear deformation via tensile
was applied to the kink, the DIC analyses indicated that the shear strains were concentrated in the kinkbands. The shear strains on the left and right bands had different signs from each other. Moreover, when
the shear deformation via compression was applied to the kink, the direction of shear strain applied wasreversed from that of the tensile. The introduction of shear strains is considered the cause of the change
in the Frank vectors, as described above.
References[1] K. Hagihara et al., Mater. Sci. Eng. A 763 (2019) 138163.
[2] T. Inamura, Acta Mater. 173 (2019) 270-280.

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Deformation Behavior of Nb2Co7
as Crystal-Structure-Based Mille-feuille Structured Material
Konatsu Yamada1*, Toshiaki Horiuchi1, Shigeru Saito1, Ken-ichi Ikeda2, Seiji Miura2 and Frank Stein3
1

Hokkaido University of Science, Maeda7-15-4-1, Teine-ku, Sapporo, Hokkaido 006-8585, Japan
2
Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan
3
Max-Planck-Institut für Eisenforschung GmbH Max-Planck-Straße 1, D-40237 Düsseldorf, Germany*Email: 9222003@hus.ac.jp
The binary intermetallics, Nb2Co7, with layered mC18 crystal structure shows excellent compressive
deformability and high strength [1,2] and is expected to be a new crystal-structure-based mille-feuillestructured (MFS) material like the LPSO phase found in Mg alloys. However, deformation mechanism of
Nb2Co7 still remains poorly understood. In the present study, deformation behavior and microstructural
evolution of Nb2Co7 are investigated mainly focusing on the kink formation and kink strengthening
phenomenon in Nb2Co7.
The Co-22.2at.%Nb alloy was vacuum induction melted, and was cut into 1.2×1.2×2.5 or 2×2×4mm3
rectangular parallelepiped specimen. The samples were heat-treated at 1000°C for 50h to attain singlephase Nb2Co7. Uniaxial compression tests at room temperature were carried out with a strain rate of either
3.75×10-4 or 1.0×10-4 s-1. Microstructure and crystallographic orientation relationship were investigatedby SEM and EBSD before and after compression tests.
The compressive stress-strain curve of Nb2Co7 is shown in Fig. 1. Nb2Co7 shows plastic deformability
and work hardening. Shown in Fig. 2. is the microstructure of the compressed sample with 0.2% plasticstrain observed by SEM. The kink-like structure without delamination was observed on the side surfaceof the sample. The detailed EBSD analyses clarify that such kink-like structure forms along the basal(001) plane with the rotation axes of (hk0) and that the rotation angles are varied, which is importantcharacteristics of kink. The excellent compressive deformability of Nb2Co7 could be achieved byoperation of basal (001) slip, twinning and kink formation. It is thus concluded that Nb2Co7 is a new
crystal-structure-based MFS material.

Fig. 1. Compressive stress-strain curve of Nb2Co7.

Fig. 2. SEM microstructure of Nb2Co7 after
the compression of 0.2% plastic strain.

Acknowledgement
The authors would like to thank Mr. Kenji Ohkubo at Hokkaido University. This work was supported
by JSPS KAKENHI for Scientific Research on Innovative Areas “MFS Materials Science” (Grant
Numbers JP18H05482).
References[1] A. Leineweber et al.: Intermetallics, 25 (2012), 34-41.
[2] L. Siggelkow et al.: Materials Science and Engineering A, 497 (2008), 174-180.

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Orientation dependence of various properties of textured MAX phase ceramics fabricatedby slip casting under strong magnetic field
Jotaro Muraoka1, Ken-ichi Ikeda1*, Seiji Miura1
Koji Morita2, Tohru S. Suzuki2, and Yoshio Sakka2
1
Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo, Hokkaido, 060-8628, JAPAN
2
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, JAPAN*Email: ikeda.ken-ichi@eng.hokudai,ac.jp

MAX phase ceramics―ternary carbides or nitrides expressed by the general formula Mn+1AXn (M:transition metal, A: group A element, X: C and/or N, n=1,2,3) have unique properties that combine
metallic (thermal and electrical conductivity, plastic deformability) and ceramic (thermal shock andoxidation resistance, low density). Since the properties of the MAX phases are anisotropic because of its
hexagonal and layered structure, texturing the MAX phases can improve properties and add
anisotropy[1]. In addition, the layered materials including the MAX phases can form a buckling
structure called as kink band, which enables material strengthening.
In this study, therefore, we fabricated textured Ti₂AlC and Ti₃SiC₂ MAX phase ceramics using slip
casting in strong magnetic field alignment followed by spark plasma sintering (SPS) [2,3]. Vickers
hardness test, high-temperature compression, and high-temperature oxidation tests were carried out toevaluate the orientation dependence of room temperature deformation behavior, kink band formation,and oxidation behavior.
The slurry was made by mixing commercial MAX phasepowder (Ti₂AlC or Ti₃SiC₂), ethanol as a solvent, andPolyethyleneimine as a dispersant. Green bodies were obtainedby slip casting of the slurry under a rotating magnetic field for
Ti₃SiC₂ and a static magnetic field for Ti₂AlC (Fig.1). A
magnetic field B of 12T was applied. The green bodies weresintered with a SPS machine at 1150℃ for Ti₂AlC and 1300℃
for Ti₃SiC₂. For Vickers hardness tests, the sintered bodies were
cut to an angle of 0~90° with c-axis. The orientation
dependence of Vickers hardness was evaluated from the SEM
images of the indent. For introducing the kink bands, eachsample was compressed perpendicular to the c-axis at hightemperatures, and the amounts of kink bands were evaluatedusing SEM-EBSD technique. High-temperature oxidation tests Fig. 1. Schematic of slip castingunder(a) rotating and (b) static
were conducted at 1100℃ for 4 and 24 h in air.
Fig. 2 shows the optical micrographs of Vickers indent tested magnetic fields.
in Ti2AlC. Vickers indent shows anisotropic shape andhardness changed depending on the loading angle against
the c-axis. Kink band formation was confirmed in thesample tested at high-temperature compression. The oxide
scale growth rates were different between Ti₂AlC andTi₃SiC₂, and its anisotropy was observed depending on theangle with the c-axis.
Acknowledgments
This work was supported by JSPS KAKENHI (Grant
Numbers JP19H05115, JP21H00087, JP21H00110, Fig. 2. Optical micrographs of Vickers
indents in Ti₂AlC by loading 49 N
JP18H05482).
paralleltoc-axis(left)
andReferences
perpendiculartoc-axis(right).
[1] X.H. Wang, Y.C. Zhou., J. Mater. Sci. Technol, 26[5](2010), 385-416.
[2] C.F. Hu, Y. Sakka, et al., J. Am. Ceram. Soc, 94 (2011), 742-748.
[3] N. Hashimoto, K. Ikeda, et al., Mater. Trans., 63 (2022), 133-140.

-86-

Mille-feuille Structures in Al-RE Eutectic Alloys and Its Kink Formation
1

Kosaku Hakita1, Ken-ichi Ikeda1, Seiji Miura1*
Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo, Hokkaido, 060-8628, JAPAN*Email: miura@eng.hokudai.ac.jp

Introduction
In order to verify the occurrence of kink strengthening in the materials composed of two-phase lamellar
structure, eutectic Al alloys with rare earth elements are prepared in the present study. FCC-Al forms
eutectic lamellar structure with tri-aluminide phase Al3RE such as Al3Y and Al3Er. By substituting Y in
Al3Y with Eu, the crystal structure of Al3RE changes from BaPb3 type to Ni3Ti type to Al3Ho type.
Stacking sequence of each of them are denoted by hhc, hc and hchcc: it means Al3(Y, Er) has partly HCP
type stacking [1]. Because of the similarity of the crystal structure among fcc Al and these tri-aluminide
phases, it was expected that the close-packed planes of Al and Al3RE are the phase boundary of Al/Al3RE
lamellar structure. It may satisfy one of the fundamental ideas, i.e., the “Mille-feuille conditions”:
dislocations in the soft layer moves along the soft layer-hard layer boundary, because these tri-aluminide
phases include partially hcp stacking which stop the motion of the dislocation on the plane not-parallel tothe phase boundary of Al/Al3RE lamellar structure. This crystallographic relationship between Al and trialuminide phases strongly restricts the dislocation motion in Al along only the phase boundary of
Al/Al3RE lamellar structure, which is similar with the dislocation motion in Zn only on the basal slip,
resulting in the formation of kink in the lamellar structure.
Experimental procedures
In the present study several Al/Al3RE two-phase alloys are prepared by Ar-arc melting machine fromhigh purity elements. Alloy composition are Al-3 at.%(Y, Er) and the composition of the tri-aluminides
are designed to be Al3Y1-xErx(x=0, 0.1, 0.5, 0.67, 1). Samples are cut, mounted and polished, thensubjected to optical microscopic observation, SEM observation and composition analysis of phases by
EDS, confirmation of crystal structure of phases by XRD, and investigation of crystallographic orientation
relationship between Al and tri-aluminides using EBSD. Compression tests using the rectangularparallelopiped samples with the size of 2 x 2 x 4 mm are conducted at room temperature with a strain rateof 2.8×10-3 s-1. The sample side surfaces are investigated before and after the compression tests using
SEM to confirm the kink formation during the plastic deformation process.
Results and Discussion
A well-developed fine lamellar structure is confirmed to be formed in all of the alloys as the result of
eutectic solidifications. The composition of primary phase together with the average composition oflamellar area enables us to establish the partial ternary phase diagram near the Al corner. EBSD analysis
revealed that the close-packed planes of Al and beta Al3Y are the phase boundary of Al/ beta Al3Y lamellar
structure, and kink formation during plastic deformations are confirmed in alloys.
Reference[1] J. H. N. van Vucht, K. H. J. Buschow, J. Less-Common Metals, 10(1966) 98-107.
Acknowledgements
This work was supported by JSPS KAKENHI (Grant Number JP18H05482) and “Nanotechnology
Platform Program” of the Ministry of Education, Culture, Sports, Science and Technology (MEXT),
Japan, (Grant Number JPMXP09A20HK0022).

-87-

Fabrication of Al2O3-GAP eutectic ceramics with fine anisotropic microstructure by flash
event and deformation behavior
Yuta Aoki1*, Hiroshi Masuda1, and Hidehiro Yoshida1
The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, JAPAN*Email: aoki-yuta4649@g.ecc.u-tokyo.ac.jp
Remarkable mechanical strength has been observed in LPSO-Mg alloy by introducing kink band in themille-feuille structure [1]. Aiming to apply this strengthening technique to structural ceramic materials,
we attempted to fabricate multiphase ceramics with a pseudo-mille-feuille structure by using eutectic
reaction. In the present study, we focused on Al2O3-GdAlO3(GAP) eutectic ceramics, which are composedof a hard Al2O3 phase and a relatively soft GAP phase. We have successfully fabricated fine anisotropic
Al2O3-GAP eutectic microstructure by using a flash sintering technique; flash sintering enables the almost
immediate densification of green compact of oxide ceramics at a relatively low furnace temperature under
an electric field above a critical strength [2]. Increased electric conductivity in oxide ceramics is anothercharacteristic of the “flash sintering” events. The increased conductivity causes significant Joule heating
and abrupt raising of specimen temperature. The plastic deformation behavior of the present eutectic
sample was evaluated by micropillar compression tests.
Commercially available high-purity Al2O3 and Gd2O3 raw powders were mixed by ball-milling at theeutectic composition of Al2O3-23 mol% Gd2O3. The powder mixture was cold-isostatically pressed andcalcined at 1450°C × 2 h in air. The dimension of the calcined sample was 1.4 mm × 3.8 mm in crosssection and 23 mm in length. The calcined sample was heated up to 1400°C in air, and a sinusoidal voltageof 1000 V/cm at a frequency of 1 kHz was applied from an AC power supply with the current limit of
110 mA for 40s, and then the external power supply was turned off. As a result, we successfully obtained
anisotropic fine eutectic microstructure. From the eutectic region of the sample, micropillar with adiameter of 1 µm and a height of approximately 2.5 µm was fabricated by focused ion beam (FIB). For
comparison, micropillar composed of Al2O3 single crystal was also produced from coarse Al2O3 single
crystal grain in the same specimen with the [0001]Al2O3 axis 20°declined from the compression
direction. Micropillar compression test was performed at room temperature at a constant strain rate (1 ×
10-3 s-1) using a nanoindenter equipped with a flat-end diamond tip. The microstructure was observed byscanning electron microscopy (SEM) and transmission electron microscopy (TEM).
The flash event resulted in partial melting of the calcined sample through the current path, wherein an
anisotropic eutectic microstructure was formed with rod-like GAP phases aligned in Al2O3 single crystals.
The average interphase spacing was approximately 170 nm in the finest area, which was comparable tothe finest spacing reported in the literature [4]. The TEM observation demonstrated that the orientation
relationship of both phases in this area were [0001]Al2O3 // [010]GAP for the growth direction.
In the micropillar compression tests, the pillar of the Al2O3 single crystal showed brittle fracture at
the compressive stress of 20 GPa, while the pillar composed of the Al2O3-GAP eutectic specimen
showed plastic deformation of about 3 % with strain hardening after yielding at about 8 GPa. This result
suggests that microscopic plastic deformation can occur in the high-strength ceramics by introduction offine multiphase microstructure. Interphase delamination did not occur even after the plastic
deformation.
References[1] Y. Kawamura, Materia Japan, 54 (2015) 44-49.
[2] M. Cologna, B. Rashkova, R. Raj, J. Am. Ceram. Soc., 93 (2010) 3556-3559.
[3] H. Su, Q. Ren, J. Zhang, K. Wei, B. Yao, W. Ma, G. Fan, M. Guo, L. Liu, H. Bai, H. Fu, J. Eur.
Ceram. Soc., 37 (2017) 1617-1626.

-88-Effect of a high-pressure press on the strength and the morphorogy of PP
Yukino Ito*, Shotaro Nishitsuji, Hironari Sano, Takashi Inoue, Hiroshi Ito
Graduate School of Organic Material Science Yamagata University
4-3-16 Jonan Yonezawa Yamagata 992-8510 Japan
Tel: +81-23-26-3086*
Email: yukino.chocolate.11@gmail.com【Introduction】
Polypropylene (PP) is an excellent crystalline polymer with ductility, good processability, and so on.
However, the strength of PP is not enough. In order to be more widely used, the high strength of PP isneeded. In development of high strength PP, there are many study by using the rolling. But, in the case ofrolling, the stress at break is low in perpendicular to the rolling direction. In other words it is affected by
the processing direction and becomes an anisotropic sample. In this study, we tried to increase theisotropic high strength of PP by using the highpressure press below the melting point. In addition,
We studied the effect of high pressure press on themorphology of PP.
【Experiment】
The polymer used in this study was a EA9(iPP) madeby Japan Polypropylene Corporation. The density is
0.90 g/cm3. The melting point is 167 ℃. Melt flow rate
MFR=0.5 g/10min. A 2 mm thick PP sheet was
produced for pelletized PP using a manual hydraulicheating press. The sheet compressed by 100 t lab
machine. The compression temperature was 120 ℃,
the compression load was 30-1000 kN(43-1400
MPa) 。 Mechanics test of sheet was tensile test.
Tensile speed was 10 mm/min. We used SAXS,WAXS, OM, and TEM to analyze the hierarchicalstructure of the higher-order crystal structure.
【Result and discussion】
Figure. 1. shows tensile stress-strain curves of as
mold PP and compressed PP by various pressure. The
stress at break was more than 3 times higher than thatof as mold samples. Also, the strength increases as
the pressure increased.
Figure. 2. shows long period, lamella thickness andcrystallinity obtained from SAXS and WAXS as afunction of pressures. As mold PP is shown at pressureof 0 MPa. The long period increase but lamella
thickness and crystallinity doesn’t change by press. In

addition, these parameters doesn’t change aspressure increases. On the other hand, crystallinityof the compressed PP didn't change from as mold PP.
In other words, the molecular chains of the amorphous
phase affects the strength of PP.
【Conclusion】
In this study, succeeded in increasing strength PP bycompression. In addition, we understand, the reason
for the strength of PP is that the molecular chains of
the amorphous phase have an effect. The details of therelationship between high strength and higher-order
crystal structure will be introduced on the day.

-89-

Effect of Compression Molding of Co-Extruded PS/PBT Multilayered Film on Crystal
Structure and Mechanical Properties
Akinori Iwamura1, Shotaro Nishitsuji1, Yutaka Kobayashi2, Akira Ishigami1, 2, Hiroshi Ito1, 2, *1
Graduate School of Organic Materials Science, Yamagata University, Japan
2
Research Center for GREEN Materials & Advanced Processing, Yamagata University, Japan*
E-mail: ihiroshi@yz.yamagata-u.ac.jp
Kink strengthening phenomenon has been firstly discovered in a long-period stacking-order (LPSO)
structured Mg alloy that revealed unusually high strength beyond theoretical predictions. The LPSO
structure can be generally observed as a mille-feuille structure, which is formed by alternate stacking of
microscopic hard and soft layers. The Kink strengthening phenomenon has been recently expected tostrengthen polymer materials. This research aimed to develop a mille-feuille structure based on reinforced
polymer materials and to investigate the effect of compression molding on the mechanical and structuralproperties of the mille-feuille polymer.
Polystyrene (PS) and polybutylene terephthalate (PBT) were utilized as a hard and soft layer,
respectively. The PS containing oxazoline groups was used to improve the interfacial adhesion between
PS and PBT. A 32-layered PS/PBT film and a 16-layered PBT film were prepared using a multilayer coextruder. Each of ten-layered film was adhered using a heat press to produce a 320-layered PS/PBT sheet
and a 160-layered PBT sheet. Finally, the fabricated sheets were pressed under various high pressures at
60 °C. Small-angle X-ray scattering (SAXS) and transmission electron microscope (TEM) were
performed for structural observation. Differential Scanning Calorimetry (DSC) and Wide-Angle X-ray
Diffraction (WAXD) were performed for structural analysis. Three-point bending test was performed toevaluate toughness properties.
Fig. 1 shows 2D SAXS patterns of the edge direction of the samples and TEM images in PBT layer.
From the 2D SAXS patterns, a typical pattern was observed from the virgin sheet, meanwhile, fourcharacteristic patterns were observed after the compression molding process. This could be assumed thatfolding structures were formed in the lamella structure within the PBT. From the TEM images in PBTlayers, it was confirmed that the lamellae in the PBT layer was folded, and kink structures were formed
in both sheets. It was also confirmed that the angle of folding was different between the 320-layered
PS/PBT sheet and the PBT 160-layered sheet. Fig. 2 shows the relationship between toughness obtained
from a 3-point bending test. Although the mechanical properties of PS/PBT were affected by the load, nodirect correlation of the SAXS patterns and TEM images were observed.
These results indicated that compression molding formed folding structures in the lamellae of PBT,
and the angles of folding structures of PS/PBT and PBT were different. Furthermore, compression
molding affects the mechanical properties and crystal structure of mille-feuille polymer sheets.

Fig. 1 2D SAXS patterns and TEM images in PBT layer,（a）PS/PBT before compression,（b）PS/PBT after compression, Fig. 2 relationship between pressing load
and toughness（c）PBT before compression,（d）PBT after compression
Acknowledgments: This study was partially supported by JSPS KAKENHI for Scientific Research on
Innovative Areas “MFS Materials Science” (Grant Numbers JP18H05483).

-90-

Changes in the Elastomeric Mechanical Properties of Lamellae-Forming Block
Copolymer Specimens by Introduction of Kink
1

Y. Kokuryo1 *, H. Yabu2, H. Takagi3, N. Shimizu3, N. Igarashi3, S. Sakurai1
Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan; 2 Tohoku University, 21-1, Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan; 3 High Energy Accelerator Research
Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan, *Email:m1661003@edu.kit.ac.jp[Introduction] In recent years, "kink strengthening phenomenon" has been discovered in the fieldof the metallic alloy. Kink is a region where crystals are sharply bent. We consider the possibility ofapplying this concept to polymeric materials and are focusing on block copolymers that form lamellar
microdomains consisting of hard and soft components. Previous investigations in our laboratory haveused non-oriented lamellar microdomains, and the kink was introduced by uniaxial stretching, a methodthat destroys the internal structure. To date, material strengthening through introduction of kinks has notbeen achieved. In this study, we focused on the changes in the elastomeric mechanical properties of theblock copolymer by the introduction of kink and examined whether the kink strengthening is realized.
[Experimental] The specimen used for this study is a polystyrene-block-polybutadiene-blockpolystyrene triblock copolymer. The S/B volume ratio of this sample is 56/48. As for the molecular weight,
Mn = 6.31 x 104 and Mw/Mn = 1.15. The specimens were cast from solutions using the selective solvents(mixtures of n-heptane and dichloromethane, which are selectively good solvents for PB (polybutadiene)and for PS (polystyrene), respectively). Note that the mixtures of n-heptane and dichloromethane wereused for more precise control of the degree of solvent selectivity to PS and PB. To analyze the nanostructures in the as-cast and annealed specimens along with the uniaxial stretching, two-dimensional
small-angle X-ray scattering (2d-SAXS) measurements and tensile test were simultaneously conducted atroom temperature. The measurements were performed mainly at BL-15A2 of Photon Factory at HighEnergy Accelerator Research Organization (KEK). The X-ray wavelength was 0.118 nm and the camera
length was 3200 mm. A PILATUS2M was used as the 2-dimensional detector. The tensile test was
performed with an initial chuck distance of 10 mm. Tensile speed was 6 mm/min.
[Results and Discussion] The stress-strain curves shown in Fig. 1 were obtained, based on the fivespecimens results of the off-line SS measurements in our laboratory. Fig. 1 indicates that the kinked
material (the curve(a)) was not clearly strengthened. Although it shows the highest stress of the earlystage of the strain among all specimens, the specimen was not elongated well so that the elongation atbreak is not high enough and either the stress at break was not high as compared to the curve (c). Notehere that the kink formation was detected by the simultaneous SAXS measurements for the case of thecurve (a) during the period where the stress remained constant due to the macroscopic necking of thespecimen. The stress level at this stage may be related to the fracture of the hard (glassy) PS lamellae. It
is interesting to find that the final strain of the necking depends on the individual specimens. As for the
D0 specimen (the curve (a)), the stage of the constant stress level (necking) was shortest among all
specimens. To understand what determines this length, the results of the simultaneous SAXS
measurements were helpful. As a result, the manner of the fracture of the PS domains differs dependingon the microdomain orientation. The details will be explained on site. It isalso noteworthy that the slope of the SS curve at the later stage (successive
to the stage of the constant stress level) is almost similar to each other for
all specimens examined in this study. Although it may be considered thatthe rubbery PB chains mainly contributes to the stress as such rubberypolymer chains are elongated with the aid of the fragmented PS
microdomains which play a role of the physical crosslinking points, the SS
curve in the reversing process (by releasing the load from the specimen)
Fig.1 Stress-strain curves for thewas found to be not coincident with the forwarding process. Actually, the as-cast specimens. The curve (a)for the specimen prepared byreversing process exhibited much lower stress. This clearly reminds the is
the solution cast using dichloromore proceeding of the fracture or crazing of the fragmented PS domains in methane. The curve (b) is for the
specimen prepared by the solution
the microscopic level. The correlation between these mechanical properties cast using solvent mixture of nheptane/
dichloromethaneand nanostructural changes will be reported also on-site.
(25:75) and (c) is for the case of
the mixture of (75:25).

-91-

Strengthening mechanism of crystalline polymer by heat elongation
Mamoru Endo1*, Daisuke Egusa1, Hiromu Saito2, Katsumi Hagita3, Eiji Abe1,4
1
The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, JAPAN2
Tokyo Univ. of Agriculture and Technology, 2-24-16, Nakacho, Koganei-shi, Tokyo, 184-8588, JAPAN3
National Defense Acad. of Japan, 1-10-20, Hashirimizu, Yokosuka-shi, Kanagawa, 239-8686, JAPAN
4
National Institute for Materials Science, 1-2-1, Sengen, Tsukuba-shi, Ibaraki, 305-0047, JAPAN*Email: endo@stem.t.u-tokyo.ac.jp
Crystalline polymers have hard lamellae crystalline layers and soft amorphous layers, and they arealternately stacked to form a layered microstructure termed as the lamellae stack. The material properties
are expected to be improved by controlling the lamellae stack structure.
In recent years, it has been reported that some crystalline polymers become strengthened by heatelongation. In the case of high-density polyethylene (HDPE) [1], the heat elongation process significantly
increases yield strengths of the HDPE whose degree depends on the heat elongation ratio. X-ray
diffraction analysis using HDPE suggests that this strengthening originates from the alignment of lamellae
stacks orientations and shortening of lamellae crystal length [1], but details of the microstructure and thestrengthening mechanisms are still unclear.
In this study, we investigated the microstructure of HDPE based on transmission electron microscopy(TEM). We prepared the extruded HDPE films by blown film extrusion process, and the elongated HDPE
films were obtained by heat elongation of extruded films at 373 K up to various elongation ratio. The
samples were thinned by the microtome method, stained with ruthenium tetroxide solution at room
temperature, and subjected to TEM observation.
Fig. 1 shows TEM images acquired from the extruded HDPE film, and inverse Fourier transformed
image reproduced from a specific frequency domain in the power spectrum. Since staining with ruthenium
tetroxide preferentially introduces heavy metals into amorphous materials, we identified that brightcontrasts in the TEM image correspond to crystalline layers in the lamellae structure. Inverse Fouriertransformed image with contrast enhancement corresponding to lamellae stack confirms that lamellae
stacks form an oriented microstructure in the extrusion direction of the extruded HDPE. After headt
elongation with a ratio of 400%, the lamellae crystal length decreased while the orientation of the lamellae
stacks increased (Fig. 2).
The above results are consistent with the structure predicted from small-angle X-ray scattering
reported previously [1]. We will discuss details on the deformation mechanisms of lamellae stack before
and after heat elongation in the presentation.

a

a

b

EX

b

ED

Fig. 1 (a) TEM bright field image of extruded
HDPE and its FFT pattern. EX corresponds tothe extruded direction. (b) Inverse FFT imageof the specific frequency domain.

Fig. 2 (a) TEM bright field image of elongated
HDPE (elongation ratio: 400 %) and its FFTpattern. ED corresponds to the elongation
direction. (b) Inverse FFT image of the specificfrequency domain.

Reference[1] T. Murayama et al., Polymer, 236 (2021), 124343.

-92-

~MEMO~-93-

Development of hcp/bcc layered structure in Mg-Sc alloy
and kink formation by compression
Yukiko Ogawa1*, Akiko Nakamura1, Rintaro Ueji1, Satoshi Emura1,
Toru Hara1 and Hidetoshi Somekawa1
1
Research Center for Structural Materials, National Institute for Materials Science,
1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, JAPAN*
Email: OGAWA.Yukiko@nims.go.jp
Recently, high strength Mg alloys with Long-Period Stacking Order structure (LPSO-Mg) weredeveloped and their high strength was reported to be due to kinking at the LPSO phase which consistsof multilayer of hard layers and soft layers [1-3], called mille-feuille structure. Therefore, to obtain kinkstrengthening in other alloy, the investigation for how to develop mille-feuille structures and how toform kink in the obtained mille-feuille structures is required.
According to Mg-Sc binary phase diagram, bcc phase is stable in high temperature region and hcp
phase is stable in low temperature region at the Sc content of over around 18 at%. In fact, themicrostructure of Mg-Sc alloy is known to be controlled by heat treatment through phase transformation[4]. Layered hcp/bcc structure is reported to be obtain in Ti alloy which shows hcp/bcc phasetransformation as with Mg-Sc. That hcp/bcc layered structure in Ti alloy is formed though cold rollingand subsequent heat treatment for the process of hcp precipitation [5]. Based on these backgrounds, weinvestigated the microstructure of Mg-Sc developed by cold rolling followed by heat treatment and kinkformation in the developed hcp/bcc layered structure in Mg-Sc.
In this study, the Mg-Sc ingot with the nominal composition of Mg-30 wt%Sc was used. The
semi-circle shaped plate with the thickness of about 25 mm was cut from the ingot and that plate was
hot rolled at 873 K to obtain 5 mm thick plate. Then, the hot rolled plate was annealed at 963 K for 0.5
h followed by water quenching to obtain bcc single phase. The bcc single phase plate was cold rolled
and then heat treated for the hcp precipitation. Compression test was carried out for the kink formation
with a strain rate of 10-2 s-1. The microstructure was observed by optical microscope and SEM.
After cold rolling with a thickness reduction of 5~10% followed by annealing at 893 K for 10 min,the hcp/bcc layered-like structure in which the precipitated hcp phases glowed particular direction ineach bcc grain was obtained (Fig.1). The precipitated hcp and bcc had a Burgers orientation relationshipand the hcp was found to preferentially precipitate at the slip lines which formed in bcc during coldrolling.
By 20% compression at room temperature, kinking was observed at a part of region of hcp/bcc
layered sample.
References[1] Y. Kawamura et al., Mater. Trans. 42 (2001)
1172-1176.
[2] E. Abe et al., Acta Mater. 50 (2002) 3845-3857.
[3] K. Hagihara et al., Intermetallics 18 (2010)267-276.
[4] Y. Ogawa et al., Mater. Sci. Eng. A 670 (2016)335-341.
[5] S. Emura and X. Ji, Mater. Trans. 61 (2020)
856-861.

50 μm

Fig. 1. Optical microscope image of Mg-Sc 5% coldrolled followed by annealing at 893 K for 10 min.

-94-

Effect of Additional Element on Nonflammability of LPSO type Mg-Zn-Y Alloy
Shin-ichi Inoue1*, Kazumasa Iwanaga1, Michiaki Yamasaki1, and Yoshihito Kawamura1
1
Kumamoto University, 2-39-1, Kurokami, Chuo-ku, Kumamoto, 860-8555, JAPAN*Email: shinoue7@kumamoto-u.ac.jp
Mg alloys have been attracting keen attention as promising lightweight materials for aerospace,automobile, and railway applications. On the other hand, it is often pointed out that Mg alloys havepoor oxidation resistance and burn easily. This flammability of Mg alloys is a problem to be solved
when we consider using Mg alloys as structural materials of mass transportation vessels. In fact,
the Federal Aviation Administration (FAA) in the USA banned the use of Mg alloys for aircraft cabins.
However, from point of view of reducing aircraft weight, FAA decided to lift the ban on using the Mg
alloy in an aircraft cabin and set up a flammability test for Mg alloys. As a part of development ofnonflammable Mg alloy, some metal elements have been added into Mg alloys. It has long been
known that the addition of rare earth elements can improve incombustibility of the surface of theoxide film on Mg alloy [1-4]. Among the RE-containing Mg alloys, Mg-Zn-Y alloy with a long period
stacking order (LPSO) phase has excellent mechanical properties and is expected to be used inaircraft components. LPSO-type Mg-Zn-Y alloy produced by rapidly solidified powder metallurgy has
an extremely high yield strength of ~600 MPa. LPSO-type Mg-Zn-Y alloy produced by ingot
metallurgy and extrusion has a multimodal microstructure, and high yield strength of ~400 MPa [5,6]. In addition, the Mg97Zn1Y2 alloy exhibits an ignition temperature of 1150 K [7, 8]. However, this
ignition temperature is lower than the FAA oil burner temperature, so further improvement in
ignition temperature is required to safely use LPSO-type Mg-Zn-Y alloys. It has been reported thatthe addition of some elements such as Be, Yb, Ca, and Sr improved the ignition temperature of Mg
alloys [8-10]. In this study, we attempted to improve the ignition temperature of LPSO-type Mg-ZnY alloys by addition of Be, Yb, Ca, and Sr.
Mg-Zn-Y-X alloys (X = Ca, Yb, Be, and Sr) were prepared using high-frequency induction melting
in Ar atmosphere. Ignition temperature measurement was performed using TG/DTA. The heating
rate was 50 K/s. Specimens were heated at 973 K in a muffle furnace in air. For investigating thestructure of oxide films, XRD measurement, SEM, and TEM observation were conducted on a crosssection of the film formed on the Mg-Zn-Y alloys.
With the addition of Ca, Yb, Be, or Sr, the Mg-Zn-Y alloys exhibited an ignition temperature of
approximately 1300 K. XRD measurement and SEM observation revealed that the surface film of
the alloy was mainly composed of Y2O3. In the case of Ca or Yb-containing alloys, outer CaO andYb2O3 layer formed on the Y2O3 film. Furthermore, Be and Sr were concentrated in the Y2O3 film [8].
Thin and uniform Y2O3 film without internal oxidation of Y was observed in Ca, Yb, Be, or Srcontaining Mg-Zn-Y alloys from SEM observation. This suggests that addition of Ca, Yb, Be, or Sr,helps to form high protectivity Y2O3 film on the surface of Mg-Zn-Y alloy by suppressing internaloxidation and abnormal growth of Y2O3 film.

References[1] B. S. You et al., Scr. Mater. 42 (2000) 1089-1094.
[2] M. Sakamoto et al., J. Mater Sci. Lett. 16 (1997) 1048-1050.
[3] B. H. Choi et al., Met Mater. Int. 9 (2003) 395-398.
[4] Q. Tan et al., Scr. Mater. 115 (2016) 38-41.
[5] Y. Kawamura et al., Magnesium Technology 2005, (2005) 499-502.
[6] Y. Kawamura et al., Mater. Trans. 47 (2006) 959-965.
[7] S. Inoue et al., Corros. Sci. 174 (2020) 108858.
[8] S. Inoue et al., Corros. Sci. 149 (2019) 133-143.
[9] S. Inoue et al., Corros. Sci. 122 (2017) 1188-122.
[10] D.S. Aydin et al., J. Mater. Sci. 48 (2013) 8117-8132.

-95-

Creep characterization of a long period stacking ordered Mg85Zn6Y9 alloy
1

Hidenari Takagi1*, Mayumi Suzuki 2
Division of Applied Physics, Department of General Education, College of Engineering, Nihon
University, 1 Nakakawahara Tokusada Tamura Koriyama, Fukushima, 963-8642, Japan.
2
Department of Mechanical Systems Engineering, Faculty of Engineering,
Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama, 989-0398 Japan*
Email: takagi.hidenari@nihon-u.ac.jp[Introduction] A new type of Mg alloy, with a mille-feuille structure, is stronger than the conventionalalloys due to the laminated structure of the soft and hard layers, and the introduction of a deformation
band called a kink band (KB). Hagihara et al. showed that a KB introduced during deformation provided
high resistance for dislocation motion in the temperature range from room temperature to approximately
300 °C. 1) In addition, nanoindentation tests at room temperature were conducted on KBs, which
determined that a KB contributed to a higher hardness level 2) or KB played the role of relaxation sites for
dislocations 3). In this study, we evaluated the creep properties of the Mg85Zn6Y9 alloy via an indentation
technique at 250 °C and 300 °C and investigated the role of KBs in creep deformation.
[Experimental Methods] A rectangular piece of the unidirectional solidified (DS) Mg85Zn6Y9 alloy was
cut and shaped to approximately 3 × 8 × 2 mm via emery polishing. KBs were introduced by rolling thealloy in the 2 mm-thick DS direction at a reduction ratio of 0.2. The indentation creep tests were conductedat the test surface (2 × 8 mm) after the rolled alloy was polished with emery paper. Subsequently, thealloy was annealed at 320 °C for 24 h and then polished with colloidal silica to remove the surface oxide
layer. The indentation creep tests were conducted at 250 °C and 300 °C at the indentation creep rates from10 -3 to 10 -6 s -1 using a microindenter (Advance Riko, Inc.)[Results] Figure 1 shows the stress dependence of the indentation creep rate at 250 °C and 300 °C. For
the high creep rates at 250 °C, the stress exponent, n, which was the slope of the data, was equal to 9.
When the creep rate was low, the stress dependence of the indentation creep rate was weak. This result
indicated that there was limited stress for deformation such as threshold stress. For 300 °C, the n-value
from 1 x 10-3 to 4 x 10-5 s-1 is similar to that of the low creep rates at 250 °C. However, in the low creep
rates at 300 °C, the stress dependence of the indentation creep rate was more pronounced and the n-value
was approximately 3.5. According to the conventional creep theory, the n-value of 3.5 demonstrated thatthe dislocation motion was the creep-rate controlling mechanism; therefore, the KB had a different effecton the dislocation motion at 250 °C compared to 300 °C in this experiment.
[References] 1) K. Hagihara et al, Acta Mater. 163 (2019) 226–239. 2) K. Morita et al, Annual Reportof MFS Research in FY2021, pp. 270-273. 3) T. Hoda et al., Annual Report of MFS Research in
FY2021 (Poster Session).
[Acknowledgments] This work was supported by the Grant-in-Aid for Scientific Research "Materials
Science on mille-feuille structure" (JP21H00107).
10-2

10-2

10-3

.

.

10-4

10-5

10-6

10

100

Stress, σs

Mg85 Zn 6 Y9 (DS, r = 0.20 + 320℃,24h)s !1

T = 250℃

Indentation creep rate, e s /Indentation creep rate, e s /s !1

Mg85 Zn 6 Y9 (DS, r = 0.20 + 320℃,24h)1000

T = 300℃

10-3

10-4

10-5

10-6

10

100

Stress, σs/ MPaFig. 1. Stress dependence of the indentation creep rate

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1000

/ MPa

Observation of Kink Deformation in an LPSO Mg85Zn6Y9 Alloyusing Two-directional Micro-Laue Diffraction Mapping under Compression
1

Shigeru Kimura1*, Kazushi Sumitani1, and Kentaro Kajiwara1
Japan Synchrotron Radiation Research Institute, 1-1-1, Kouto, Sayo-cho, Hyogo, 679-5198, JAPAN*Email: kimuras@spring8.or.jp

Ternary magnesium (Mg)–transition metal (TM)–rare earth (RE) alloys with long-period stackingordered (LPSO) structures, which are formed by synchronizing structural modulation and chemicalenrichment of TM and RE atoms, are paid much attention as lightweight structural materials because of
their extraordinary mechanical properties such as high strength and high ductility [1-6]. These excellent
mechanical properties are believed to be due to the unique deformation behavior—referred to as “kinkdeformation”—of the LPSO phase [5].
Synchrotron-radiation (SR) micro-Laue-diffraction (MLD) mapping is a unique technique forvisualizing grain boundaries with 10-μm-order spatial resolution [7,8]. MLD mapping can reveal internal
grain boundaries, which cannot be observed by electron backscatter diffraction (EBSD). It is thus a key
means of studying deformation of those boundaries.
To investigate the deformation behavior of the LPSO phase of Mg polycrystal, we developed a compact
compression-test stage for SR-MLD measurements, which can compress a small sample with a size of
0.3 mm × 0.3 mm× 1.0 mm. The compression-test stage was used for SR-MLD mapping experiments at
the white x-ray diffraction beamline (BL28B2) of SPring-8. In the experiments, change in the grainboundary was successfully visualized by changing the compression load [9]. However, depth information
could not be obtained because projection images could be obtained from only one direction.
Aiming to obtain that depth information, in the present work, we therefore modified the compact
compression-test stage so that grain-boundary images could be taken from two orthogonal directions. As
a result of this structural modification, it became possible to obtain depth information concerning the
kink-formation position. Also, change in surface morphology of the sample could be observed
simultaneously by using an optical microscope to compare bulk and surface images.
Comparing the grain-boundary images with the surface-morphology photographs revealed kinkdeformation in the grain-boundary images but no change in the surface-morphology photographs. Thisobservation demonstrates the advantage of SR-MLD measurements compared to the surface sensitive
measurements such as optical microscopy, scanning electron microscopy, and EBSD.
References[1] Y. Kawamura, K. Hayashi, A. Inoue and T. Masumoto, Mater. Trans. 42 (2001) 1172-1126.
[2] A. Inoue, Y. Kawamura, M. Matsushita, K. Hayashi and J. Koike, J. Mater. Res. 16 (2001) 18941900.
[3] Y. Kawamura,T. Kasahara, S. Izumi and M. Yamasaki, Scripta Mater. 55 (2006) 453-456.
[4] Y. Kawamura and M. Yamasaki, Mater. Trans. 48 (2007) 2986-2992.
[5] K. Hagihara, N. Yokotani and Y. Umakoshi, Intermetallics 18 (2010) 267-276.
[6] K. Hagihara, A. Kinoshita, Y. Sugino, M. Yamasaki, Y. Kawamura, H.Y. Yasuda and Y.
Umakoshi, Acta Mater. 58 (2010) 6282-6293.
[7] K. Kajiwara, M. Sato, T. Hashimoto, I. Hirosawa, T. Yamada, T. Terachi, T. Fukumura and K.
Arioka, Phys. Status Solidi A 206 (2009) 1838-1841.
[8] K. Kajiwara, M. Sato, T. Hashimoto, T. Yamada, T. Terachi, T. Fukumura and K. Arioka, ISIJInternational 53 (2013) 165-169.
[9] S. Kimura, K. Kajiwara and T. Shimura, Jpn. J. Appl. Phys. 55 (2016) 038002.

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Phase transformation behavior of LPSO structure during annealing
investigated by in-situ neutron diffraction
1

Wu Gong1*, Kazuya Aizawa1, Stefanus Harjo1, and Takuro Kawasaki1
J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki,319-1195, Japan*
Email: wu.gong@j-parc.jp

Recently, a new class of dispersion strengthened magnesium alloys has attracted high attention due totheir excellent mechanical properties [1]. A long period stacking ordered (LPSO) phase in these alloys
contributing to the enhanced strength and ductility has been clarified. The LPSO phase includes polytypicstructures such as 14H, 18R, 24R, and 10H [2]. These polytypic LPSO structures can coexist with otherprecipitations in the Mg–RE–TM system depending on chemical composition and temperature. In orderto clarify the stability and the structure evolution of LPSO phase at high temperature, an as-cast
Mg85Zn6Y9 alloy with duplex LPSO structure of 18R and 10H was investigated by in-situ neutron
diffraction during annealing. In-situ neutron diffraction experiments were performed by BL19 ‘TAKUMI’of Japan Proton Accelerator Research Complex (J-PARC). Fig.1(a) shows the geometrical arrangementof the in-situ heating test. A cylindrical specimen with an 8-mm diameter and 16-mm length was set upon the high temperature frame horizontally, with its length direction oriented at +45 to the incident neutron
beam. Two detector banks with 5-mm-wide radial collimators positioned at +90° and −90° relative to theincident beam were used to collect the neutron diffraction patterns, which correspond to the axial andradial directions of the specimen, respectively. Fig.1(b) shows the heating history, that the specimen washeated to 300 °C at a rate of 5 °C /min and then up to 550 °C at a rate of 2 °C /min for 2 hours isothermal
holding followed by furnace cooling. Neutron diffraction profiles during the whole process were
continuously collected in an event recording mode by two detector banks simultaneously. The temperature
was measured by a thermocouple attached to the specimen. A 10H-LPSO to 18R-LPSO structuretransformation was observed during heating. The evolutions of phase fraction and lattice parameters were
estimated quantitatively from the diffraction profiles, and these results will be discussed to reveal thephase transformation behavior in the as-cast Mg85Zn6Y9.

Fig. 1 (a) Geometrical arrangement of in-situ neutron diffraction experiment at TAKUMI, J-PARC.
(b) Temperature history of the heating test.
References[1] Kawamura, Y., Hayashi, K., Inoue, A., Masumoto, T., Mater. Trans. 42(2001)1172–1176.
[2] Abe, E., Ono, A., Itoi, T., Yamasaki, M., Kawamura, Y., Phil. Mag. Lett., 91(10)(2011)690-696.

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Development of 4D in-situ observation system for the investigation of kink development
during compression of Mg-based LPSO alloys
1

Masayuki Uesugi1
Japan synchrotron radiation research institute (JASRI/SPring-8)
Email: uesugi@spring8.or.jp

A new setup was developed for 3D observation of kink development in Mg-based LPSO alloys
utilizing sample load apparatus and grain boundary imaging with synchrotron radiation X-ray CT, toinvestigate the relationship between formation of kink structure and strain and stress. Using this setup,
Mg85Zn6Y9 material was compressed, and kink development was observed as a time series of CT data
(4D, 3D + time series).
Figure 1 shows the images of the sample load apparatus. Rotating stages above and below thespecimen rotate synchronously. The specimen was compressed by the Z-stages which also locatedabove and below the specimen. This configuration allows the specimen to be rotated for CT observation
with compressed. Experiments were carried out using 40 keV X-rays generated by a multilayer mirror at
BL20B2@SPring-8. The X-ray beam monitor includes a CMOS camera (ORCA Lightning, Hamamatsu
Photonics) with 4608x4608 pixels. The number of CT projections was 3600, and the CBP method wasused for image reconstruction. The specimen was a piece of Mg85Zn6Y9, cut into 0.2 mm thick and 1.5mm x 2 mm. The experiment was performed in step by step flow. The specimen was observed by CT,then compressed along with observation with transmitted X-ray image. Then the CT observation was
performed again. The specimen was compressed 3 steps with 10 µm for each step.
Figure 2 shows the result of the 30 µm compression. Formation of a kink on the surface of thespecimen (righthand-side of the figure) could be observed. The kink structure was also observed inside
the specimen, through the bending of grain boundaries. The direction of the grain boundary bending
indicates that this structure was formed by the movement of the material to the left in the figure. In
contrast, another kink was observed on the back side of the specimen surface but same position, which
formed through the movement of the material to the right. This is opposite direction to that of front side.
The results indicate that the kink structures in this specimen occurred by pushing materials outward
from the sample surface by compression. Because the material was extruded in opposite directions fromboth sides of the thin specimen, kinks on the front and back surfaces show opposite direction. Thus,
multiple kink structures were formed in correlation.
This experiment demonstrated that the new 4D in-situ observation system has sufficient capability toobserve kink development. In future improvement, a load cell will be introduced to enable morequantitative analysis. In addition, we plan to apply the digital volume correlation method (DVC) toautomatic recognition of kinked structure from CT data to enable statistical discussions.

Fig. 2 CT images of specimen. Dashed lines show
shape of kink structure and black arrows show
bended grain boundaries.

Fig. 1 Schematic illustration and an image ofsample load apparatus.

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Electronic structure of Mg-Zn-Y cluster in dilute Mg alloys studied by STEM-EELS
Yohei K. Sato1* , Daisuke Egusa 2 , Hidetoshi Miyazaki3 , Koji Kimura 3 , Mitsuhiro Itakura4 , Masami
Terauchi1 and Eiji Abe1, 2
1
IMRAM, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai, 985-8577, JAPAN2
The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, JAPAN3
Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, 466-8555, JAPAN
4
Japan Atomic Energy Agency, 178-4-4, Wakashiba, Kashiwa, 277-0871, JAPAN*Email: y-sato@tohoku.ac.jp
In solute enriched stacking faults (SESF) in Mg-Zn-Y alloys with a long-period stacking ordered(LPSO) structure, the formation of Zn6 Y8 clusters was confirmed [1]. Recently, synthesis of a singlecrystal Mg alloy with dilute solute of Zn and Y has been reported, where SESFs are sparsely distributedin the hcp-Mg matrix [2]. Although clusters composed of Zn and Y atoms appear to exist in the dilute
Mg-Zn-Y alloy, the cluster structure has not been determined using usual structural analysis methods
because of random arrangement of clusters due to the low concentration in SESF. Recently, structural
analysis using X-ray fluorescence holography (XFH) has been carried out and the presence of Mg3 Zn3 Y8cluster structure in dilute Mg-Zn-Y alloy has been proposed. On the other hand, the electronic structuresof the clusters in the dilute and the LPSO Mg-Zn-Y alloys has not been investigated. In this study, electronenergy-loss spectroscopy (EELS) combined with scanning transmission electron microscopy (STEM)
was applied to the dilute (Mg99.2 Zn0.2 Y0.6 ) and LPSO (Mg75 Zn10 Y15 ) Mg alloys to clarify the electronic
structures of the clusters in SESFs for both Mg alloys. In particular, the momentum transfer (q) resolved
EELS measurements have been carried out to investigate the anisotropic electronic structure in dilutealloys.
Fig. 1A shows the Y-L3 absorption spectra obtained from SESF of Mg99.2 Zn0.2 Y0.6 . The spectra wereshown for q parallel to the ab-plane (q//ab) and c-axis (q//c) directions of the hcp structure. The spectrumof q//ab has an additional structure around 2080 eV, which was not observed for q//c, indicating theanisotropic feature of the Y-L3 spectra. The spectral simulations using the cluster structure model(Mg3 Zn3 Y8 ) proposed by STEM and XFH analysis also showed anisotropy feature. On the other hand,
the Y-L3 spectra (Fig. 1B) obtained from Mg75 Zn10 Y15 were almost isotropic. These results suggest thatthe electronic structure of thecluster of the dilute Mg alloy isdifferent from that of the Zn6 Y8cluster.
Furthermore,thedifference of electronic structures
between two Mg alloys indicatesthat the cluster structure of thedilute Mg alloy should be
different from the Zn6 Y8 clusterin the LPSO Mg alloy. The factthat the ELNES simulation in Fig.
1A agrees with the experimentindicates that the cluster model(Mg3 Zn3 Y8 ) is a valid structure.
Reference[1] D. Egusa et al., Acta
Materialia, 60, 166-178 (2012).
[2] K. Hagihara et al.., Acta
Materialia, 209, 116797 (2021).

Fig.1A: Anisotropic Y-L3 spectra of Mg99.2 Zn0.2 Y0.6 . Momentum
transfer q were directed along ab in-plane direction (q//ab) and along
c-axis direction (q//c). Fig 1B: Isotropic Y-L3 spectra ofMg75 Zn10 Y15 .

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DFT Calculation of Kink Boundary Migration in LPSO Structure1

Mitsuhiro Itakura1, Masatake Yamaguchi 1, Daisuke Egusa2, and Eiji Abe2
Japan Atomic Energy Agency, 178-4-4 Wakashiba, Kashiwa, Chiba 277-0871, Japan
2
The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan*

Email: Itakura.mitsuhiro@jaea.go.jp

Kink boundaries formed in Mg-based long period stacking order (LPSO) alloys play a key role instrengthening of these materials. As the kink structure grows, many high-angle kink boundaries are
eventually formed which has inclination angle close to 34 degrees. We show that this peculiar structure
is a result of irreversible structural transformation and is energetically stable. We also calculatesegregation energies of alloying elements Y and Zn to this boundary. Segregation energy is greater forZn case and the maximum value is about 0.7eV. Finally, the critical resolved shear stress for the
migration of kink boundary is estimated for a pure-Mg kink and that with saturated with segregation.
We show that segregated kink boundary requires very high shear stress about 700 MPa for migration.
Figure 1(a) shows high-angle kink boundary saturated with Zn and Y atoms, which occupy
segregation sites estimated by DFT calculation. The color of atoms indicates stacking order A, B and C
in the 18R structure as shown in Fig.1(b), and apparent asymmetry with respect to the boundary can be
seen. This asymmetry is induced by irreversible relaxation of the boundary structure. Fig.1(c) shows
stress-strain relation for the applied shear stress acting on the kink boundary. Without solute atoms, thecritical resolved shear stress (CRSS) for boundary migration is about 400 MPa, whereas saturation ofsolute atoms increases the CRSS to about 700 MPa. In the actual LPSO structure where hard soluteclusters prevent local shuffling of atoms, the CRSS for boundary migration should be much higher andexpected to be irrelevant to plastic deformation.
References[1] Y. Kawamura et al., Mater. Trans. 42, 1172 (2001).
[2] D. Egusa and E. Abe, Acta Mater. 60, 166 (2012).
[3] K. Hagihara et al., Intermetallics 18, 267 (2010).
[4] T. Inamura et al., Acta Mater. 173, 270 (2019).

Fig.1 (a) Atomistic configuration of 34-degree kink boundary in 18-R LPSO structure. Colors of
atoms indicate their coordinate in the direction vertical to the figure, as shown in (b). (c)Stress-strain
relation for the applied shear stress acting on the kink boundary with and without solute atoms. The
drops in stress correspond to migration of kink boundary.

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First-Principles Study on the Electronic Origin of Phase Stability in Mg-Zn-Y alloys
with a Long-Period Stacking Order
Takao Tsumuraya1*, Hiroyoshi Momida2, and Tamio Oguchi3
Magnesium Research Center, Kumamoto University, Kumamoto 860-8555, Japan
2
The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
3
Center for Spintronics Research Network, Osaka University, Toyonaka 560-8531, Japan*
Email: tsumu@kumamoto-u.ac.jp
1

A dilute Mg-1Zn-2Y (at%) alloy exhibits a tensile yield strength of ∼600 MPa [1]. This strength iscoupled with the appearance of a unique crystal structure called the long-period stacking order (LPSO),
where solute atoms of Zn and Y are enriched in a few layers of the (0001) plane of the hexagonalclose-packed Mg matrix, and Shockley partial dislocation occurs in the solute atoms enriched layer. The
stacking faults order periodically, and their stacking sequence is relatively long along the [001] directionof the hexagonal lattice [2]. Furthermore, structural analysis using transmission electron microscopy(TEM) revealed that L12-type clusters of solute elements are embedded in the Mg matrix near the
stacking fault [3]. This study examines the origin of the phase stability of the 18R LPSO structure using
first-principles density-functional theory calculations. Generally, the density of states (DOS) of metals
with an hcp structure is characterized by a deep valley (pseudo gap) around the Fermi energy [4,5]. The
depth of the valley in DOS represents the magnitude of splitting of the peaks in the occupied andunoccupied states, which is an energy separation between the bonding and antibonding orbitals [4]. By
comparing the electronic structures between hcp Be and hcp Mg, Inoue and Yamashita suggested thatthe degree of energy splitting between the two main peaks (the width of the DOS valley) appears as adifference in the enthalpy of formation between the metals [5]. In this study, the heat of formation as afunction of the number of Zn vacancies is calculated to evaluate the role of Zn atoms. The calculated
convex hull indicates that the Zn atoms in LPSO are stable even at about half of the Y atoms. The
partial density of states of Mg atoms nearest to the Zn atoms forms a valley structure due to the bonding
state with Zn atoms, leading to the stability of the LPSO structure [6].
References[1] Y. Kawamura, K. Hayashi, A. Inoue, and T. Masumoto, Mater. Trans. 42 (2001) 1172.
[2] E. Abe, Y. Kawamura, K. Hayashi, and A. Inoue, Acta Metall. 50 (2002) 3845.
[3] D. Egusa and E. Abe, Acta Mater. 60 (2012) 166.
[4] T. Tsumuraya, I. Watanabe, and T. Sawaguchi, Phys. Rev. Research 3 (2021) 033215, and thereferences therein.
[5] S. Inoue and J. Yamashita, J. Phys. Soc. Jpn. 35 (1973) 677.
[6] T. Tsumuraya, H. Momida, and T. Oguchi, Appl. Phys. Express 15 (2022) 075506.

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Experimental Investigation on Kink Strengthening of Biotite Single Crystals:
Rank-1 Connection and Surface Dislocation
Hiroyuki Nagahama1*, Tom Ofune1, Eranga Jayawickrama1,2, Jun Muto1
1
Tohoku University, 6-3, Aoba, Aramaki, Aoba-ku Sendai, Japan
2
Hiroshima University,1-3-1 Kagamiyama, Higashi-Hiroshima City, Hiroshima, Japan*Email:hiroyuki.nagahama.c7@tohoku.ac.jp
Materials science has pointed out that kink formation in Mille-feuille structures can lead to kinkstrengthening, which strengthens beyond the intrinsic strength of the material [1, 2]. A previous study [3]reported that shear occurs in finite slip planes in long-period stacking-ordered (LPSO) structures, anddeformations that satisfy rank-1 connections (Hadamard’s compatibility) form kink bands. An analogue
experiment of kink formation in layered rocks [4] showed that strain hardening occurs with kink formation.
However, it is not clear whether similar kink strengthening occurs in real rocks. It is also unclear whetherrock kink formation is induced by shear at restricted slip planes [5], similar to the LPSO structure. In thisstudy, we performed deformation experiments on biotite single crystals, a layered mineral that plays animportant role in strengthening the crust, and investigated kink formation and kink strengthening byobserving the stress-strain behavior and microstructure, and discuss the relationship between rank-1
connections and surface dislocations [6].
A high-pressure and high-temperature gas apparatus installed at Tohoku University was used.
Experimental conditions were selected in the order of temperature (°C), confining pressure (MPa), andcrystal orientation as follows: 1) 300℃, 10MPa, [010], 2) 300℃, 100MPa, [010], 3) 600℃, 100MPa,[100], 4) 600℃, 100MPa, 45° to [010], and 5) 300℃, 185MPa, [010]. Note that all samples werecompressed parallel to the above directions. In addition, scanning electron microscopy (SEM) was used
to observe the microstructures of the deformed samples under the conditions of 300 °C, 10 MPa, [010]and 300 °C, 185 MPa, [010]. From the stress-strain curves of each experiment, we observed that strain
hardening occurred immediately after yielding. As the confining pressure increases from 10 MPa to 100
MPa and 185 MPa, both the yield stress and the ultimate stress increase while the stress decreases withtemperature. Microstructural investigation revealed the formation of kink bands in both samples deformed
under 300 °C, 10 MPa, [010] and 300 °C, 185 MPa, [010] conditions. Moreover, comparing the kink bandorientation and the stress field according to a previous study [2], it was observed that the matrix rotates
due to kink formation. In this experiment, axial compression was performed parallel to the basal plane of
biotite, so the matrix phase should be parallel to the maximum compressive stress after kink bandformation [2]. The kink band boundary has a symmetric tilt boundary. This indicates that the mechanism
by which kink bands are formed in the LPSO structures by satisfying rank 1 connections [3], equivalent
to the surface dislocations [6], may also apply to biotite. A previous study [2] reported that yielding andkink formation are likely to occur in the part of the foliated structure with a slight initial gradient of theslip plane, so the result indicates that the initial gradient of the slip plane may cause shear and kink bandformation occur by a mechanism similar to that of the LPSO structure. In future investigations, we will
perform microstructural analysis of the samples before deformation to observe how the slight initial
gradient of the slip surface contributes to kink formation. In addition, we need to understand how kinkstrengthening, known in materials science, affects the strength of the lithosphere.
References[1] Hagihara, K., Ueyama, R., Tokunaga, T., Yamasaki, M., Kawamura, Y., Nakano, T., Materials
Research Letters, 9 (2021) 467-474.
[2] Hagihara, K., Ueyama, R., Yamasaki, M., Kawamura, Y., Nakano, T., Acta Materialia 209 (2021)
116797.
[3] Inamura, T., Acta Materialia 173 (2019) 270-280.
[4] Weiss, L. E., In: Baer, A J., Norris, D.K. (Eds.), Proceedings Conference on Research in Tectonics.
Canada Geological Survey, Ottawa. Paper 68-52 (1968) 294-357.
[5] Moreira,N., Dias, R., Journal of Structural Geology 156 (2022) 104550.
[6] Bullough, R., Bilby, B. A. Proc. Phys. Soc. B 69 (1956) 1276.

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Shape of Local Buckling in Cu/SBS Stacking Films Subject to Compressive Deformation
Yoshihisa Kaneko1*, Yuuto Horii1, Makoto Uchida1, Kentaro Taki2 and Hiroshi Yabu3
1
Department of Mechanical Engineering, Osaka Metropolitan University,
Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, JAPAN
2
Department of Frontier Engineering, Kanazawa University, Kakuma, Kanazawa 920-1192 JAPAN3
WPI-AIMR, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, JAPAN*
Email: kaneko@omu.ac.jp
To investigate buckling behavior of metal/polymer stacking structures, we conducted compressive teston thin films consisting of alternate stack of copper and styrene-butadiene-styrene (SBS) block
copolymer layers fabricated on annealed copper substrates. The copper layers were deposited byelectroless plating and the SBS layers were painted by dip coating technique. By alternating theelectroless plating and the dip coating, we obtained the several films of Cu/SBS staking structure
consisting of six layers. The thickness of the copper layer varied from 0.2 µm to 1.5 µm, while the SBS
layer thickness was set at the constant value of 0.25 µm. The copper substrates with the Cu/SBS film
were shaped to square pillar samples (3´3´6 mm3) for compressive test. The Cu/SBS film was coatedon one of four longitudinal substrate surfaces. Compressive strain of 10% was imposed along thelongitudinal axis in air at room temperature.
Figure 1a shows a typical surface of the Cu/SBS film after the compressive test. Surface relieves
extending perpendicular to the compressive axis are visible. A cross section machined by FIB milling isshown in Fig.1b. It is clear that each surface relief is owing to a local buckling of the stacking film. The
buckled film was detached from the copper substrate. This should be because fracture strength of thebottom SBS layer is poor.
To investigate the effect of the copper-layer thickness on occurrence frequency and the buckling shape,
we measured the average spacing between adjoining bucklings, the height and width values of thebucklings. The average spacing increased linearly with increasing copper-layer thickness. This agree
well with the theoretical wavelength of sinusoidal deformation of a single metallic film that is deposited
on a soft polymer substrate [1]. Both height and width of the bucklings increased with increasing
copper-layer thickness. However, the observed bucklings revealed wide variation in both height andwidth. This scattering of the buckled shapes is attributed to different growths of the respective bucklings.
To eliminate the buckling growth affection, we paid attention to the minimum buckling width at eachcopper-layer thickness: the minimum buckling width probably corresponds to the buckling width atnucleation. The minimum buckling width was linearly proportional to the copper-layer thickness. Thischange in the minimum buckling width can be explained by the elastic buckling of component copper
layers.

Fig. 1. SEM images showing (a) the surface and (b) the cross section of acompressed Cu/SBS stacking film.
References[1] H. Jiang, D-Y. Khang, J. Song, Y. Sun, Y. Huang and J.A. Rogers: Proc. Natl. Acad. Sci. 104(2007)
15607-15612.

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Elastic properties in a Ti3SiC2 MAX phase with a nanolayered crystal structure
Masakazu Tane1*, Ruxia Liu2, Hajime Kimizuka3, Yuji Shirakami4, Ken-ichi Ikeda5, Seiji Miura5, Koji
Morita6, Tohru S. Suzuki6, Yoshio Sakka6, Lianmeng Zhang7, and Tohru Sekino2
1
Graduate School of Engineering, Osaka Metropolitan University, 3-3-138 Sugimoto, Osaka, 5588585, Japan
2
SANKEN, Osaka University, Ibaraki, Osaka 567-0047, Japan3
Department of Materials Design Innovation Engineering, Graduate School of Engineering, Nagoya
University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
4
Division of Materials Science and Engineering, Graduate School of Engineering, Hokkaido University,
Kita-13, Nishi-8, Kita-ku, Sapporo, 060-8628, Japan
5
Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University, Kita-13,
Nishi-8, Kita-ku, Sapporo, 060-8628, Japan
6
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan
7
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan
University of Technology, Wuhan 430070, PR China*
Email: mtane@omu.ac.jp
A Ti3SiC2 phase is an important MAX phase, exhibiting excellent plastic deformability [1,2] and highYoung’s modulus (~340 GPa). The Ti3SiC2 MAX phase has a nanolayered crystal structure, in whichTi(2)-C, C-Ti(1), and Ti(1)-Si bonding layers are stacked along the c-axis ([0001]). Notably, atomic bonding
is inhomogeneous between the layers. The bonding in C-Ti(1) and Ti(2)-C is strong owing to the covalentbonding nature combined with metallic and ionic contributions, whereas the Ti(1)-Si bonding is weak,
especially in shear deformation. Reflecting the nanolayered crystal structure and inhomogeneous atomic
bonding, the Ti3SiC2 MAX phase exhibits strong anisotropy in plastic deformation and fracture. However,
the effects of nanolayered crystal structure and heterogeneous atomic bonding on the elastic properties of
the Ti3SiC2 MAX phase have not been clarified yet despite their importance for understanding themechanical properties and atomic bonding nature in the MAX phase. One of this reason is the difficultyin growing large single crystals required for the measurement of single-crystalline elastic properties.
In the present work, the elastic properties in a Ti3SiC2 MAX phase single crystal were studied, focusing
on the effects of the anisotropic nanolayered crystal structure and heterogeneous interlayer atomic
bonding. First, we prepared polycrystalline Ti3SiC2 samples with crystallographic texture using a slip
casting technique combined with a spark plasma sintering (SPS) process. For the prepared polycrystals,
the crystallographic texture was analyzed using the X-ray pole figure, and the all the independent
components of elastic stiffness in the polycrystals with the crystallographic texture were measured using
resonant ultrasound spectroscopy (RUS) combined with electromagnetic acoustic resonance (EMAR).
Next, by analyzing the polycrystalline elastic stiffness reflecting the elastic properties of constituent single
crystals and crystallographic texture on the basis of an inverse Voigt-Reuss-Hill (iVRH) approximation,
the elastic properties of the Ti3SiC2 single crystal were determined. This revealed that the singlecrystalline elastic properties were almost isotropic despite its highly anisotropic layered structure.
Furthermore, for the Ti3SiC2, Ti3AlC2, and Ti3AlC2 single crystals, their elastic properties were analyzed
using first-principles calculations based on density functional theory (DFT). The analyses revealed thatTi(1)-Si bonding is relatively stable owing to the hybridization of the d electron in Ti and the p electron in
Si, as well as the localized electrons around the Si atom, which contribute to the isotropic elastic properties
and high elastic constants in the Ti3SiC2 MAX phase [4].
References[1] M.W. Barsoum, T. El-Raghy, J. Am. Ceram. Soc. 79 (1996) 1953-1956.
[2] C.M. Fang, R. Ahuja, O. Eriksson, S. Li, U. Jansson, O. Wilhelmsson, L. Hultman, Phys. Rev. B 74
(2006) 054106.
[3] R. Liu, M. Tane, H. Kimizuka, Y. Shirakami, K. Ikeda, S. Miura, K. Morita, T.S. Suzuki, Y. Sakka,
L. Zhang, T. Sekino, J. Eur. Ceram. Soc. 41 (2021) 2278-2289.

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Thermodynamic Evaluation and Experimental Investigation of Suzuki Effectin the Al–X Binary Systems
1

Tatsuya Tokunaga1*, Kazuki Hanada1, Ryota Suemitsu1, and Seiji Miura2
Kyushu Institute of Technology, 1-1, Sensui-cho, Tobata-ku, Kitakyushu, 804-8550, JAPAN2
Hokkaido University, Kita 8, Nishi 5, Kita-ku, Sapporo, Hokkaido,060-0808, JAPAN*Email: tokunaga@post.matsc.kyutech.ac.jp

As mille-feuille structures (MFS) with alternating layers of hard and soft layers, it has been proposedthat they can be classified into the crystal structure-based MFS (single phase with two layers), which
consists of stacking at the atomic level as seen in Mg alloys with the synchronized long period stacking
ordered (LPSO) structure, the microstructure-based MFS (two-phase with two layers) based on
two-phase equilibrium, , and their hybrid type MFS [1]. Recently, the segregation behavior of solute
elements to stacking faults in Mg97Y2Zn1 (at.%) alloy containing LPSO structures has been
thermodynamically evaluated by Umebayashi et al. [2] applying the Hillert’s parallel tangent law [3].
Fundamental information on the formation of stacking faults in the matrix phase and the segregation
behavior of solute elements to the stacking fault regions (Suzuki effect [4]) is indispensable for thedesign of novel alloys with crystal structure-based MFS.
In this study, the effects of alloying elements on the Suzuki effect and the stacking fault energy in the
fcc matrix phase for Al–X (X: Ag, Cu, Zn) binary alloys were thermodynamically evaluated using thefirst-principles calculations and the CALPHAD method. In the application of Hillert's parallel tangent
law, the hcp phase was regarded as stacking faults in the fcc matrix phase. The stacking fault energy
was evaluated based on the treatment proposed by Olson and Cohen [5]. According to the calculated
results, it was predicted that the Al–Ag and Al–Cu alloy had a high segregation tendency of solute
elements to the stacking fault region, in contrast, the Al–Zn alloys showed no segregation tendency of asolute element. In addition, the stacking fault energy in the Al–Ag alloy would be significantly reducedwith increasing Ag content. Detailed of the results of microstructural observation using TEM for Al–Ag
alloys will be presented.
References[1] S. Miura, A. Ishizaka and K. Ikeda, Collected Abstracts of the 2019 Autumn Meeting of the Japan
Inst. Metals and Materials, (2019) S3.30 (DVD) (in Japanese).
[2] T. Umebayshi, S. Iikubo and H. Ohtani, J. Japan Inst. Met. Mater. 78 (2014) 117-125 (in Japanese).
[3] M. Hillert, Lectures on the theory of phase transformations, H. I. Aaronson ed., AIME, New York,(1975) 36-44.
[4] H. Suzuki, Sci. Rep. Inst. Tohoku Univ., A 4 (1952) 455-463.
[5] G. B. Olson and M. Cohen, Metall. Trans. A 7 (1976) 1897–1904.

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Kinking in Compression of Pearlitic Steel and Resultant Plastic Anisotropy
Rintaro Ueji *, Hidetoshi Somekawa, Satoshi Emura and Tadanobu Inoue
Research Center for Structural Materials, National Institute for Materials Science,
1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan*
Email: UEJI.Rintaro@nims.go.jp
Pearlitic structure consisting of lamellar ferrite and cementite is one of the fundamental microstructure
in steel and it has some preferable properties such as preferable resistance against hydrogen embrittlement[1]. It has been clarified that the kinking occurs during the compression of pearlitic steels [2], indicating
the potential of advanced microstructural control to achieve preferable mechanical properties. Pearlitic
structure provides the anisotropy of strength due to its morphology and it is unclear whether the kinking
changes this anisotropy. The aim of this work is to clarify the effect of the deformation microstructures
including kinked lamella on the plastic isotropy of pearlitic steel.
A spring steel (SAE9254; Fe - 0.55C - 0.7Mn - 0.76Cr - 1.48Si [wt%]) was studied. The pearlitic
structure was prepared by the heat treatment with the austenitization at 950 °C followed by isothermal
holding at 700 °C. Double compression test [3] was conducted to clarify the plastic anisotropy whichmeans, in this work, the dependence of yield stress on the loading direction. The 1st compression with acylindrical test piece (8 mm in diameter and 12 mm in height) was applied so as to evolve deformation
microstructure such as kinking. The loading directions of the second compressions were set parallel orperpendicular to that of the first compression. The perpendicular loading was realized by the cutting of
the first compressed sample to rectangle shape. In both loading directions, the flow stress at the 2ndcompression increased with increasing of the strain applied by 1st compression. When compared atsimilar strain by the 1st compression, the 2nd flow stress at the perpendicular loading was smaller thanthat at the parallel loading. This difference keeps even after the 1st compression (~30%) enough to obtainthe kinking [2], indicating the kinking appears keep the plastic isotropy.

Fig. 1. Stress - strain curves obtained by the double compression test of the spring steel with pearlitic
structure. The loading direction of the 2nd compression was parallel (a) and perpendicular (b) to that of
the 1st compression.
References[1] R.Ueji, Y.Kimura, T.Inoue, ISIJ Int., 62(2022) 368.
[2] R.Ueji, H.Somekawa, T.Inoue, T.Hara, Mater. Sci Eng. A, 857(2022) 144018.
[3] K.Hagihara, M.Yamasaki, Y.Kawamura, T.Nakano, Mater. Sci. Eng. A, 763(2019) 138163.

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