bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Particle Size Distribution of the Feedstock Powder on the Microstructure of Bulk Metallic Glass Sprayed Coating by HVOF on Aluminum Alloy Substrate
Authors: Kim Hyun Guen , Nakata Kazuhiro , Tsumura Takuya , Sugiyama Masaharu , Igarashi Takanori , Fukumoto Masahiro , Kimura Hisamichi , Inoue Akihisa
Published: March 2009

The Fe-based bulk metallic glass (Fe43Cr16Mo16C15B10) sprayed coating with the thickness
about 220%m was successfully deposited on an aluminum alloy (A5052) metal substrate using an
HVOF (High Velocity Oxygen Fuel) spraying process. All sprayed coating has still kept the
amorphous state after spraying. The Fe-based bulk metallic glass coating shows good adhesion to
the aluminum alloy metal substrate, and has a high hardness with HMV 913~1120. It has been
found that better properties can be obtained in the sprayed coating by using finer powder.
Effect of Hydrogen Concentration at Overlay / Base Metal Interface on Repair Weldability of Petroleum Pressure Vessel
Authors: Mori Hiroaki , Nishimoto Kazutoshi , Kayano Rinzo
Published: March 2009

In order to extend the life of petroleum pressure vessels operated in long term, it is
demanded to establish the repair welding technique. To make clear the effect of weld thermal cycles
during repair welding on the hydrogen content and weld cold cracking at the base metal of 2.25Cr-
1Mo steel / overlaying metal of austenitic stainless steels interface in the structural material of
petroleum pressure vessels, the crack susceptibility was estimated by y-groove weld cracking test
and repair welding test with varying overlay thickness and hydrogen exposure conditions. In
addition, the hydrogen distribution in the material was calculated by the theoretical analysis using
the diffusion equation based on activity. The crack susceptibility was raised with increase in the
hydrogen content at the interface. It was concluded that the cracking could be prevented by
controlling the repair welding process to reduce the hydrogen content at the interface.
Fatigue Analysis of Stainless Steel Overlap Joining Panel Partially Penetrated by Laser Welding
Authors: Lee Kyoung Don , Park Ki Young , Ho Kwang Il
Published: March 2009

Experiment, finite element method, and theoretical analysis were performed to
understand the fatigue phenomena of stainless steel overlap joining panels of different thickness
partially penetrated by Nd:YAG Laser welding. The fatigue life curves are obtained through fatigue
tests with various levels of applied load. The fatigue life is related with parameters such as
thickness of plates, bead width, gap size, and penetration depth through experiment. To understand
the fatigue test results, the effects of local stresses around a weld bead are calculated by FEM and
theoretical stress analysis as a guide to the laser welding process control.
Strain-Induced Martensitic Phase Transformation by Low-Cycle Fatigue in AISI 316L Stainless Steel
Authors: Jeon Y.C. , Kim C.S. , Ki Ho , Kwun S.I. , Byeon J.W.
Published: March 2009

The evolution of the strain-induced α′ martensite during the cyclic deformation of
austenitic AISI 316L stainless steel (SS) was investigated. The low-cycle fatigue (LCF) test was
conducted at various strain amplitudes in air. The amount of α′ martensite was determined for the
fatigue-failed specimens as well as for the specimens interrupted after a specific number of cycles.
The volume fraction of α′ martensite increased with increasing strain amplitude and number of
fatigue cycles. The cyclic hardening behavior was discussed in terms of the dislocation density and
strain-induced α′ martensite transformation.
Weldability of Zinc Coated Steel Sheet by Plasma Arc Welding
Authors: Winarto
Published: March 2009

The use of zinc coated steel in the automotive industry is rapidly increasing as a result
of consumer demand for improved corrosion resistance of automobile bodies. Plasma arc welding
of zinc coated steels is currently under investigation, with a strong emphasis on their weldability. In
the present study, plasma arc welding has been performed on zinc coated steel with several welding
parameters, such as current, travel speed and flow of plasma gas. Those parameters are
interrelated in their effect on penetration, in order to produce sound welds. An optimum
combination of parameters was sought, which would give full penetration of the weld, with the
highest travel speed and no visual defects on every steel-sheet as a basis; hence, characterizing the
process in the most interesting way and into a useful industrial applications. It is found that zinc
coated steel sheets of 0.7 mm and 1 mm thickness can be welded by plasma arc welding. The
microstructures of welds were almost similar. There is a slight difference in chemical composition
of the welds because of zinc pick-up which varies from the top surface to the bottom welds. The
presence of zinc in the welds did not have any effect on the mechanical properties.
Forefront in High Accurate Prediction of Welding Distortion in Japan
Authors: Kim You Chul
Published: March 2009

In discussion on reduction of energy and an environmental issue on a global scale,
the research project had been organized in Japan. In the project, a committee “Development of
model for the high accurate prediction of welding distortion by computer simulation” was set up for
the purpose of reduction of energy spent for correction of welding distortion. A lot of items were
investigated. The research was carried out to find the dominant factor for the high accurate
prediction of welding distortion generated by fillet welding in the committee. As the results, two
dominant factors were found and welding distortion generated by fillet welding could be predicted
with high accuracy by satisfying two dominant factors.
Study of Weldability for Circularly Input Heat
Authors: Shirai Hideaki , Okano Shigetaka , Mochizuki Masahito , Toyoda Masao
Published: March 2009

Different techniques are being studied to make the automotive electrical parts more compact and
lightweight; along with improving their functionality for saving energy and protecting the
environment. In the wake of this trend, the joints in these parts are required to have little distortion
and a high degree of accuracy. Although laser welding, which yields low-distortion joints, was
developed in response to this demand for high accuracy, it has been difficult to meet the needs of
modern, high-accuracy automobile parts with conventional laser welding. In this research, in order
to realize that degree of accuracy, a phenomenal and theoretical analysis of the melting
solidification process was conducted and high-accuracy laser welding was investigated for
controlling welding deformation.
Magnetoelastic Nature of Ferromagnetic Shape Memory Effect
Authors: Chernenko Volodymyr A. , L'vov Victor A.
Published: March 2009

The giant magnetically-induced deformation of ferromagnetic shape memory alloys
results from the magnetic field-induced rearrangement of twinned martensite under the magnetic
field. This deformation is conventionally referred to as the magnetic-field-induced-strain (MFIS).
The MFIS is comparable in value with the spontaneous deformation of crystal lattice during the
martensitic transformation of an alloy. Although the first observations of MFIS were reported more
than 30 years ago, it has got a world-wide interest 20 years later after the creation of the Ni–Mn–Ga
alloy system with its practically important room-temperature martensitic structure and experimental
evidence of the large magnetostriction. The underlying physics as well as necessary and sufficient
conditions for the observation of MFIS are the main focus of this chapter. A magnetostrictive
mechanism of the unusual magnetic and magnetomechanical effects observed in Ni–Mn–Ga alloys
is substantiated and a framework of consistent theory of these effects is outlined starting from the
fundamental conception of magnetoelasticity and the commonly known principles of
ferromagnetism and linear elasticity theories. A reasonable agreement between the theoretical
deductions and available experimental data is demonstrated and, in this way, a key role of
magnetoelastic coupling in the magnetomechanical behavior of Ni–Mn–Ga alloys is proved. A
correspondence of magnetostrictive mechanism to the crystallographic features of MFIS and the
basic relationships of the thermodynamics of solids are discussed.
Structural and Mechanical Characterizations of Ni-Mn-Ga Thin Films Deposited by R.F. Sputtering and Heat-Treated
Authors: Bernard Florent , Delobelle Patrick , Hirsinger Laurent , Rousselot Christophe
Published: March 2009

The near-stoichiometric Ni2MnGa ferromagnetic alloys are one of these smart materials,
that show a great interest when they are deposited as a thin film by rf sputtering. These thin films of
shape memory alloys (SMAs) are prospective materials for micro and nanosystem applications.
However, the properties of the SMAs polycrystalline thin films depend strongly on their structure
and internal stress, which develop during the sputtering process and also during the post-deposition
annealing treatment. In this study, 1μm Ni55Mn23Ga22 thin films were deposited at 0.45 and 1 Pa of
Ar and their composition, crystallographic structure, internal stress, indentation modulus, hardness
and deflection induced by magnetic field were systematically studied as a function of the
temperature of the silicon substrate ranging from 298 to 873 K and the vacuum annealing treatment
at 873 K for 21 and 36 ks. A silicon wafer having a native amorphous thin SiOx buffer layer was
used as a substrate. This substrate influences the microstructure and blocks the diffusion process
during the heat treatment. The crystal structure of the martensitic phase in each film was changed
systematically from bct or 10M or 14M. In addition, the evolution of the mechanical properties such
as means stress, roughness, hardness and indentation modulus with the temperature (of substrate or
of heat treatment) were measured and correlated to crystal structure and morphology changes. It is
concluded that the response of a free-standing magnetic SMAs films to a magnetic field of 200
kA/m depends strongly on the martensitic structure, internal mechanical stress (mean and gradient)
and magnetic properties. The free-standing annealed film at 873 K for 36 ks demonstrates a
considerable magnetic actuation associated with bct or 10M or 14M martensitic structures.
A Phase-Field Simulation of Nucleation from Subgrain and Grain Growth in Static Recrystallization
Authors: Muramatsu Mayu , Tadano Yuichi , Shizawa Kazuyuki
Published: March 2009

A new recrystallization phase-field method is proposed, in which the three stages of
recrystallization phenomena, i.e., recovery, nucleation and nucleus growth are sequentially taken
into account in a computation. From the information of subgrain patterns and crystal orientations in
a polycrystal that are obtained by a dislocation-crystal plasticity FE analysis based on a
reaction-diffusion model, subgrain groups surrounded by high angle boundary are found out. Next,
subgrains in the group are coalesced into a nucleus by rotation of crystal orientation and migration
of subgrain boundaries through a phase-field simulation. Then a computation of nucleus growth is
performed also using the phase-field method on account of an autonomic incubation period of
nucleation, in which stored dislocation energy assumes a role of driving force. It is shown that the
present method can numerically reproduce the three stages of recrystallization as a sequence of
computational procedure.
Application of Strain Gradient Plasticity Modelling to High Pressure Torsion
Authors: Molotnikov Andrey
Published: March 2009

An analytical model describing the deformation behaviour of copper during the
high-pressure torsion (HPT) processing is presented. The model was developed on the
microstructural basis where the material is partitioned in two ‘phases’, the dislocation
densities in cell walls and the dislocation densities cell interior, entering the model as scalar
internal variables. The resulting ’phase mixture’ model is combined with strain gradient
theory to account for strain non-uniformity inherent in SPD.
It was demonstrated that gradient plasticity model is capable of describing the experimentally
observed trends and accounting for a homogenisation of the accumulated shear strain across
the HPT sample. The predictions of the model with respect to the ultrafine grain size
produced by HPT and evolution of dislocation densities are in good agreement with
experimental results reported by other research groups.
Numerical Modeling of Dislocation-Grain Boundary Interaction and Continuum Mechanics Analyses for Mechanical Properties of Fine Grained Metals
Authors: Ohashi Tetsuya , Tsugawa Ryota , Ogasawara Tomotaka
Published: March 2009

Macroscopic mechanical response of metal polycrystal with mean grain diameter of 0.2 to
5 microns are simulated by a strain gradient crystal plasticity software code which incorporates some
phenomenological models for dislocation accumulation and annihilation, as well as dislocation-grain
boundary interactions. Obtained results of macroscopic stress-strain relation show significant
increase of yield stress and strain hardening ratio for fine grained specimens.
Multiscale Modeling of SPD Processes for Grain Refinement
Authors: Alexandrov Igor V.
Published: March 2009

The results of a recent multiscale computer modeling are presented in this report. The
conducted investigations are devoted to the processes, which take place in different metallic
materials subjected to severe plastic deformation (SPD). It is presented that the developed models
and approaches can be useful in the successful prediction and comprehensive analysis of the
peculiarities of material flow and the ways of its homogenization, the understanding of principles of
grain structure refinement, the achievement of given grain morphology, grain boundary
misorientation spectrum and crystallographic texture, as well as in the evaluation of the active
deformation mechanisms, estimating the level of structure-sensitive properties, etc. It is shown that
multiscale modeling is a very promising approach which could supply the researchers with the
possibility to take into account the complex influence of the different parameters, related to SPD
processing and material in order to refine the grain size and obtain homogeneous bulk
nanostructured materials.
Bulk Mg Produced by Back Pressure Equal Channel Angular Consolidation (BP- ECAC)
Authors: Wu Xiao Lin , Xu Wei , Kubota Masahiro , Xia Kenong
Published: March 2009

Bulk magnesium was consolidated from pure Mg particles with an average size of ~59
µm by back pressure equal channel angular pressing. The Mg powder was processed at 200°C for 4
and 8 passes, respectively, using route C. The consolidated materials displayed density of 1.78
g/cm3, compared to the theoretical value of 1.74 g/cm3 for pure Mg. Vickers microhardness (HV)
values were measured to be about 54. Compressive tests at room temperature revealed yield
strengths of 100-110 MPa and ultimate strengths of up to 142 MPa with strains to fracture of ~9%,
comparable to those for extruded pure Mg. Microstructures were examined using optical
microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy
(TEM).
Effect of Electroplastic Deformation on Martensitic Transformation in Coarse Grained and Ultrafine Grained Ni-Ti Shape Memory Alloy
Authors: Sergeeva Anastasia E. , Setman Daria , Zehetbauer Michael J. , Prokoshkin Sergey , Stolyarov Vladimir V.
Published: March 2009

The aim of this paper is the investigation of electroplastic deformation (EPD)
and subsequent annealing influence on martensitic transformation in the shape memory Ni50.7Ti49.3
alloy. Using differential scanning calorimetry method it was shown that EPD at the low strain
stimulates structure relaxation and recovers martensitic transformation in cooling, which is usually
suppressed by cold rolling.
Double-Billet Incremental ECAP
Authors: Rosochowski Andrzej , Olejnik Lech , Richert Maria W.
Published: March 2009

Batch SPD processes have a limited scope for being used on an industrial scale. More
feasible are continuous processes among which the new SPD process of Incremental ECAP (IECAP)
is an attractive option. In this paper, a double-billet version of I-ECAP, which doubles
process productivity, is presented. The concept of the process is first checked using the finite
element (FE) method. FE simulation results are the basis for the design of an experimental rig.
Trials of nanostructuring of 10x10x200 Al 1070 billets are carried out with the forces on the
reciprocating die and the feeder measured. Metallurgical samples after 4 and 8 passes of I-ECAP
(route BC) are investigated using TEM. Tensile properties after 8 passes are established. All these
results show that the new SPD process of I-ECAP gives the results comparable to those obtained by
a classical batch ECAP with the added capability of dealing with much longer (possibly infinite)
billets.
High Strain Rate Superplasticity in a Zr and Sc Modified 7075 Aluminum Alloy Produced by ECAP
Authors: Turba Krystof , Malek Premysl , Rauch Edgar F. , Cieslar Miroslav
Published: March 2009

Equal-channel angular pressing (ECAP) at 443 K was used to introduce an ultra-fine
grained (UFG) microstructure to a Zr and Sc modified 7075 aluminum alloy. Using the methods of
TEM and EBSD, an average grain size of 0.6 1m was recorded after the pressing. The UFG
microstructure remained very stable up to the temperature of 723 K, where the material exhibited
high strain rate superplasticity (HSRSP) with elongations to failure of 610 % and 410 % at initial
strain rates of 6.4 x 10-2 s-1 and 1 x 10-1 s-1, respectively. A strain rate sensitivity parameter m in the
vicinity of 0.45 was observed at temperatures as high as 773 K. At this temperature, the material still
reached an elongation to failure of 430 % at 2 x 10-2 s-1. These results confirm the stabilizing effect
of the Zr and Sc additions on the UFG microstructure in a 7XXX series aluminum alloy produced
by severe plastic deformation.
Strain Rate Sensitivity Studies of Cryomilled Al Alloy Performed by Nanoindentation
Authors: Ahn Byung , Mitra R. , Hodge A.M. , Lavernia Enrique J. , Nutt S.R.
Published: March 2009

Al 5083 alloy powder was mechanically milled in liquid nitrogen to achieve a
nanocrystalline (NC) structure having an average grain size of 50 nm with high thermal stability,
and then consolidated by quasi-isostatic (QI) forging. The consolidation resulted in ultrafine grains
(UFG) of about 250 nm, and the bulk material exhibited enhanced strength compared to
conventionally processed Al 5083. The hardness of as-cryomilled powder and the UFG material
was measured by nanoindentation using loading rates in the range of 50−50,000 /N/s, and results
were compared with the conventional grain size alloy. Negative strain rate sensitivity was observed
in the cryomilled NC powder and the forged UFG plate, while the conventional alloy was relatively
strain rate insensitive.
Temperature Field in Severe Plastic Deformation at Small Strain Rates
Authors: Murthy Tejas G. , Huang C. , Shankar M. Ravi , Chandrasekar Srinivasan , Trumble Kevin P. , Sullivan John P.
Published: March 2009

The temperature and strain rate fields in severe plastic deformation (SPD) are measured
using infra-red thermography and Particle Image Velocimetry (PIV), respectively. Plane strain
machining is used as the method of SPD to impose controlled strains and strain rates. For metals
such as titanium, the temperature rise is small at small strain rates and SPD occurs at near-ambient
temperature. The possibility of exploring dynamic recovery/recrystallization phenomena using the
Zener-Hollomon parameter in this SPD framework is briefly discussed.
Structure of Triple Junctions of Grains, Nanoparticles in them and Bending - Torsion in Metal Nanopolycrystals
Authors: Koneva Nina , Kozlov Eduard , Popova N.A. , Zhdanov A.N. , Fedorischeva M.V.
Published: March 2009

The paper presents the results of the transmission electron microscopic (TEM)
investigation of the structure and phase composition of nanocrystalline copper obtained by the
severe plastic deformation using the high pressure torsion (HPT) method. Special attention is paid
to the triple junctions of grain boundaries. It was established that the triple junctions contained the
partial disclinations and particles of the secondary phases. The dependences of such junction
fractions on the deformation were measured of the formation at nanocrystalline copper. The phase
analyses of the secondary phase structure were carried out, the sizes of the phase particles and their
volume fractions were determined. The bending – torsion of the crystal lattice arising near the triple
junctions was measured. The problem of the long – range stress field screening was considered.
Workability Limits of Commercial Purity Titanium Subjected to Equal Channel Angular Pressing
Authors: Kumar G.V. Preetham , Uday Chakkingal
Published: March 2009

Commercial purity Ti is an important candidate material for orthopedic and dental
implants because of its high specific strength, good corrosion resistance and excellent
biocompatibility. However, for biomedical applications as a replacement for Ti-6Al-4V alloy that is
currently used, improvement in strength of CP Ti is necessary. This can be achieved by using severe
plastic deformation (SPD) processes like equal channel angular pressing (ECAP) at warm working
temperatures followed by conventional processing at room temperatures. This requires adequate
workability after ECAP. In this study, the workability of CP Ti after warm ECAP has been
investigated. Specimens of CP Ti, 17 mm in diameter, were extruded using processing route Bc
through an ECAP die with an angle of 120◦ between the two intersecting channels and at a
temperature of approximately 400oC. Workability testing was carried out using collar type
compression specimens by upsetting the specimens between flat platens till the onset of cracking.
Workability diagrams have been plotted as a function of axial and hoop strains at failure. The
results show that processing by ECAP lead to only minor reductions in workability of CP Ti. The
tensile strength is enhanced considerably by this process.
Shear Induced Low- and High-Angle Boundary Characterization Using Kikuchi Bands in Transmission Electron Microscopy
Authors: Cabibbo Marcello
Published: March 2009

Microstructure evolution with equal channel angular pressing (ECAP) using route Bc,
that is a 90° axial rotation of the billet between passes, up to 8 passes, was investigated by
transmission electron microscopy. The study has been focused on the induced development of
boundary misorientation and spacing toward microstructure refinement. Cell (low-angle) and grain
(high-angle) misorientation and spacing were determined from about 250 boundaries per pass of
ECAP, systematically using whether Kikuchi patterns or Moiré fringes, these latter where possible.
The average cell size and misorientation saturate within the first two passes. Misorientation and
spacing of high-angle boundaries decrease with the number of passes. After 8 passes, mean cell size
is ≈ 1.3 µm and the fraction of high-angle boundaries is ≈ 0.7. Differences in rate of grain structure
evolution per pass are linked to differences in ability of dislocations introduced in new passes to
recombine with the existing ones. As ECAP strain rises, the misorientation distribution develops
strong deviations from the MacKenzie distribution for statistical grain orientation. This is
interpreted as a result of the tendency to form equiaxed grains in a textured grain structure.
Microstructure of a Metal-Polymer Composite Processed by Severe Plastic Deformation
Authors: Sauvage Xavier , Malandain Jean Jacques , Hohenwarter Anton
Published: March 2009

Here we report about the microstructure of a metal-polymer composite that was processed
by severe plastic deformation. The composite was prepared by compaction of a sandwich made of
Al foils and polyethylene films. This aluminum-polyethylene composite was processed by high
pressure torsion and the microstructure was characterized by optical microscopy and scanning
electron microscopy. Our experimental data clearly show that in the early stage, the deformation is
not homogeneous within the sample, indicating that significant softening occurred. However, at
larger number of revolution the deformation progressively reaches the sample centre and the final
material exhibits an ultrafine grained composite structure.
Microstructural Characterizations of Cu Processed by ECAP from 4 to 24 Passes
Authors: Huang Chong Xiang , Yang Hua Jie , Wu Shi Ding , Zhang Zhe Feng
Published: March 2009

The microstructures of pure Cu processed by equal channel angular pressing (ECAP)
from 4 to 24 passes were investigated. It was found that the microstructures of Cu samples with a
small number of ECAP passes (4-8) were not inhomogeneous and the fraction of high-angle grain
boundary (HAGB) was low (25~43%). While for the samples with many number of ECAP passes
(12-24), the grains became more equiaxed-like and the GB misorientations exhibited double-peak
distribution with high fraction (51~64%) of HAGB. It was dislocation cells formed in large grains
of the few-pass samples, but subgrains in the many-pass samples. These characterizations suggested
that ultrafine-grained (UFG) microstructures in the few-pass samples were not fully accomplished,
while it was obtained after many passes (>12). It is believed that dynamic recovery during
processing for many passes was attributed to the formation of UFG microstructures.
UFG Microstructure Processing by ECAP from Double Electron-Beam Melted Rare Metal
Authors: Kommel Lembit A.
Published: March 2009

High purity (99.99, wt %) niobium ingots were received by double electron beam melting
technology. The specimens of pure metals with cast microstructure were processed using cold
equal-channel angular pressing (ECAP) followed by a heat treatment at around 1080 °C in vacuum
furnace for 2 h. Shear bands and microstructure evolution was studied in shear region at first pass
and at next passes of ECAP. Microstructure processing characterization was performed using light
optical and field emission scanning electron microscopy. Accompanied to microstructure the
changes of mechanical properties were determined by micro- and universal hardness testing. The
shear bands forming, evolution of large crystals to elongated laminar and dislocation fine-grain
structures during processing was characterized and discussed in view of metal hardening-softening
and viscoplastic behavior under subsequent hard cyclic straining.
Observations of Texture in Large Scale HPT-Processed Cu
Authors: Enikeev Nariman A. , Schafler Erhard , Zehetbauer Michael J. , Alexandrov Igor V. , Valiev Ruslan
Published: March 2009

Bulk nanostructured Cu samples with 20 mm in diameter and 1 mm in height were
processed by HPT at a pressure of 6 GPa by 10 rotations. Measurements of texture by means of
state-of-the-art XRD technique have been achieved in directions parallel and normal to the torsion
axis. Local texture measurements were performed by a spot size of 500 -m in steps of 3.5 mm in
order to examine the homogeneity of deformation. The texture data were resolved to shear plane and
analyzed in terms of ideal shear orientations. At both inner and outer areas of the disc plane typical
shear textures are observed. However, the intensity of components of textures at inner areas is
higher than that of outer one. These results can be interpreted in terms of dynamic lattice relaxations
rather than by heterogeneities in deformation.
Grain Boundary Radiotracer Diffusion of Ni in Ultra-Fine Grained Cu and Cu - 1wt.% Pb Alloy Produced by Equal Channel Angular Pressing
Authors: Ribbe Jens , Schmitz Guido , Amouyal Y. , Estrin Yuri , Divinski Sergiy V.
Published: March 2009

The radiotracer technique was applied for measuring grain boundary diffusion of Ni in
ultrafine grained (UFG) copper materials with different nominal purities and in a Cu—1wt.%Pb
alloy. The UFG specimens were prepared by equal channel angular pressing at room temperature.
The stability of the microstructure was studied by focused ion beam imaging. Grain boundary
diffusion of the 63Ni radioisotope was investigated in the temperature interval from 293 to 490K
under the formal Harrison type C kinetic conditions. Two distinct short-circuit diffusion paths were
observed. The first (relatively slow) path in the UFG materials corresponds unambiguously to
relaxed high-angle grain boundaries with diffusivities which are quite similar to those in the
respective coarse-grained reference materials. The second path is characterized by significantly
higher diffusivities. The experimental data are discussed to elucidate the contribution of nonequilibrium
grain boundaries in the deformed materials. Alternative contributions of other shortcircuit
diffusion paths cannot be ruled out, particularly for the Cu-Pd alloy.
Strength and Plasticity of Ultra-Fine Grained Zirconium at Low Temperatures
Authors: Tabachnikova Elena D. , Podolskiy Aleksey V. , Bengus Vladimir Z. , Smirnov S.N. , Natsik V.D. , Azhazha V.M. , Tikhonovsky M.A. , Velikodny A.N. , Andrievskaya N.F. , Storozhilov G.E. , Tikhonovskaya T.M.
Published: March 2009

Plasticity of ultra-fine grained (UFG) zirconium (grain size ~ 0.4 µm), produced by
intensive plastic deformation (IPD) - a combination of extrusion, annealing, and drawing, have been
studied within the temperature range 300 – 4.2 K in uniaxial compression. It was found that
decrease of grain sizes in the result of IPD leads to considerable increase of strength characteristics
for the UFG zirconium in comparison with coarse-grained (CG) zirconium (in 6 times at 300 K and
4 times at 77 K); and plasticity of the UFG zirconium keeps rather large (strain > 0.15). Two stages
of the strain-hardening and decrease of the activation volume for plastic flow with deformation have
been registered. A conclusion was made about the identity of basic deformation mechanisms in the
UFG and CG zirconium: simultaneous action and mutual influence of intragrain dislocation gliding
and twinning.
In Situ TEM Observations of Deformation Processes in Nanocrystalline Pd
Authors: Rösner Harald , Wilde Gerhard
Published: March 2009

In this study we show that in-situ tensile tests performed in a transmission electron microscope
(TEM) in combination with high-resolution TEM are feasible, and, that this method is appropriate
to elucidate the deformation processes in nanocrystalline materials directly. First results on
nanocrystalline Pd produced by repeated cold-rolling with intermediate folding of metal sheets are
presented revealing that the material ruptured during the in-situ tensile tests along grain boundaries.
Deformation twinning was observed in grains next to the crack indicating that the deformation
processes must have originated from the grain boundaries.
Effect of Processing Temperature on Microstructure Development during ECAP of Al-Mg-Sc Alloy
Authors: Sitdikov Oleg , Avtokratova Elena , Sakai Taku , Tsuzaki Kaneaki , Kaibyshev Rustam , Watanabe Yoshimi
Published: March 2009

Microstructural evolution taking place during equal channel angular pressing (ECAP) was
studied in a commercial coarse-grained Al-6%Mg-0.4%Mn-0.3%Sc alloy in a temperature interval 200-
450oC (~0.5-0.8 Tm). Samples were pressed using route A to a total strain of 12 and quenched in water
after each ECAP pass. Uniform fine-grained microstructures with the average grain sizes of 0.7 and 2.5
0m, are almost fully evolved at high ECAP strains at 250oC and 450oC, respectively, while ECAP at
300oC (~0.6 Tm) leads to the formation of bimodal grain structure with fine grains of around 1 µm and
relatively coarse grains of around 8 µm. The latter are developed due to the occurrence of static
recrystallization during “keeping” time in the ECAP channel and/or reheating between ECAP passes. The
microstructural development under warm-to-hot ECAP conditions is discussed in terms of the large
potential for grain boundary migration resulted from an overlapping of accelerated grain boundary
mobility at high pressing temperatures and enhanced driving force for recrystallization, which is caused by
a strong inhibition of dynamic recovery in a heavily-alloyed Al alloy.
Effects of Equal-Channel Angular Pressing on the Anisotropy of Ultrafine Copper and Titanium
Authors: Korshunov Alexander , Kaganova Irina , Polyakov Lev , Kravchenko Tamara
Published: March 2009

Annealed commercially pure copper and titanium were processed by equal-channel
angular pressing (ECAP) using routes BC and C. Pressed samples had a square section with a side
length of 8 mm. Anisotropy was analyzed based on the conventional yield strength at compression
in three mutually perpendicular directions. The tests were conducted with the as-received materials
and after different number of ECAP passes.
For copper, which is isotropic in the as-received state, considerable anisotropy manifests itself
after the first pass and holds out after the subsequent passes.
Anisotropy of as-received titanium holds out at further pressing and makes about 25 percent.
Anisotropy after all the passes is similar both for room and elevated temperature.
Anisotropy manifests itself during pressing in both routes, BC and C, although its behavior
differs for the different routes.
Nanostructured SPD Processed Titanium for Medical Implants
Authors: Valiev Ruslan , Semenova Irina P. , Jakushina Enja , Latysh V.V. , Rack Henry J. , Lowe Terry C. , Petruželka Jiri , Dluhoš Ludek , Hrušák D. , Sochová J.
Published: March 2009

Nanostructured titanium (nTi) with essential enhanced strength and fatigue characteristics is an
advanced material for dental implant applications. Nano Ti is commercially pure titanium, that was
nanostructured by a special technique of severe plastic deformation. It is bio inert, does not contain
even potentially toxic or allergenetic additives and has significantly higher specific strength
properties than any other titanium applied in dental implants. Cylindrical threaded screw implants
Nanoimplant® sized 2.4 mm in diameter and 12 mm in length were made from nTi. It is the first
application of nTi dental implant in the world reported. Recently more than 250 successful clinical
applications dealing with surgery on the front teeth were carried out. No complications were
noticed during the early postoperative period and early loading. Laboratory cytocompatibility tests
undertaken so far on mice fibroblast cells have indicated that nanocrystalline Ti surface has a
significantly better property for cell colonisation and healing of tissue consequently.
Life Time Predictions through X-Ray Defect Analysis of MEMS Devices
Authors: Neels Antonia , Niedermann Philippe , Dommann Alex
Published: March 2009

In single crystal silicon (SCSi) MEMS devices, crystalline imperfection is recognized to favor
failure. A DRIE etched SCSi structure was built to study the crystal strain profile in dependence of
the SCSi deformation by applying a mechanical force. High resolution X-ray diffraction methods
such as the rocking curve method and reciprocal space mapping were used to determine the strain as
well as the defect concentration in the crystal. The investigations also include the numerical
simulation of deformations.
Microstructure and Mechanical Properties of Al-0.5 at.% X (=Si, Ag, Mg) Alloys Highly Deformed by ARB Process
Authors: Terada Daisuke , Masui Toshiaki , Kamikawa Naoya , Tsuji Nobuhiro
Published: March 2009

Effect of solid solution elements on microstructure evolution and mechanical properties
was investigated using a high purity Al (purity 99.99%) and Al-0.5 at.% X ( X = Si, Ag, Mg ) alloys
deformed by accumulative roll bonding (ARB) process up to 7 cycles (equivalent strain of 5.6) at
ambient temperature. The ARB-processed high purity Al showed the equiaxed microstructure having
mean grain size of 750 nm. On the other hand, the microstructure of the ARB-processed Al-0.5at.%X
alloys showed lamellar boundary structures elongated along RD. The mean lamellar boundary
spacing significantly differed depending on the alloying elements, which suggested that solute atoms
had a significant effect on microstructure evolution. The difference in the grain size was regarded to
be caused by the difference in recovery processes in the alloys. The tensile strength of the alloys
increased with increasing the number of ARB cycles. In the Al-Si and Al-Ag alloys, the post-uniform
elongation increased with increasing the number of the ARB cycles. On the other hand, the elongation
of the Al-Mg hardly changed during the ARB process.
Structure and Properties of Mg-Al-Ca Alloy after Severe Plastic Deformation
Authors: Dobatkin Sergey V. , Estrin Yuri , Rokhlin L.L. , Popov Mikhail V. , Lapovok Rimma , Dobatkina Tatiana V. , Timofeev V.N. , Nikitina N.I.
Published: March 2009

Severe plastic deformation of a Mg-Al-Ca alloy resulted in different types of grain
structure. High pressure torsion (HPT) was shown to lead to the formation of a nanocrystalline
structure with a grain size of 100-200 nm, while equal channel angular pressing (ECAP) produced
ultrafine grained (UFG) or submicrocrystalline (SMC) structures, depending on the ECAP
temperature. An UFG structure with a grain size of 2-5 -m was formed at 300°C, as distinct from a
finer SMC structure with a grain size of 300-800 nm formed at a lower temperature (220°C). The
possibility of increasing the strength of the alloy in the UFG condition by a factor of 1.5-2,
combined with a reasonable level of ductility and enhanced functional properties was thus
demonstrated. ECAP of annealed Mg-Al-Ca with the formation of UFG structure was shown to lead
to increased yield strength (by a factor of 2) and enhanced tensile ductility (by a factor of 3).
Twinning, Dislocations and Grain Size in NanoSPD Materials Determined by X-Ray Diffraction
Authors: Ungár Tamás , Balogh L. , Ribárik Gábor
Published: March 2009

High resolution X-ray line profile analysis is sensitive to crystallite size, dislocation
densities and character, and to planar defects, especially stacking faults or twinning. The different
effects of microstructure features can be evaluated separately on the basis of the different
corresponding profile functions and the different hkl dependences of line broadening. Profiles of
faulted crystals consist of sub-profiles broadened and shifted according to different hkl conditions.
The systematic analysis of the breadts and shifts of sub-profiles enables X-ray line profile analysis
by using defect related profile functions corresponding to: (i) size, (ii) strain and (iii) planar faults,
respectively. It is shown that twinning can either be enhanced or weakened by severe plastic
deformation.
Texture and Grain Boundary Character Distribution during Equal Channel Angular Extrusion of some Two-Phase Copper Alloys
Authors: Suwas Satyam , Biswas Somjeet , Dhinwal Satyaveer Singh , Chattopadhyay Kamanio
Published: March 2009

In the present work, a thorough investigation of evolution of microstructure and texture
has been carried out to elucidate the evolution of texture and grain boundary character distribution
(GBCD) during Equal Channel Angular Extrusion (ECAE) of some model two-phase materials,
namely Cu-0.3Cr and Cu-40Zn. Texture of Cu-0.3Cr alloy is similar to that reported for pure
copper. On the other hand, in Cu-40Zn alloy, texture evolution in α and β (B2) phases are
interdependent. In Cu-0.3Cr alloy, there is a considerable decreases in volume fraction of low angle
boundaries (LAGBs), only a slight increase in CSL boundaries, but increase in high angle grain
boundaries (HAGBs) from 1 pass to 4 passes for both the routes. In the case of Cu-40Zn alloy, there
is an appreciable increase in CSL volume fraction.
Study of the Plastic Deformation in Nanocrystalline and Ultrafine Iron and Carbon Steels
Authors: Benito Josep Antonio , Tejedor Robert , Rodríguez-Baracaldo Rodriguez , Cabrera Jose María , Prado Jose Manuel
Published: March 2009

Samples of nanostructured and ultrafine grained steels with carbon content ranging from
0.05 to 0.55%wt. have been obtained by a warm consolidation process from mechanically milled
powders and subsequent heat treatments. In general, homogeneous grain size distributions were
obtained except for the low-carbon steel in which a bimodal grain size distribution was observed
when it was heat treated at high temperatures. The stress-strain response has been studied by means
of compression tests. Nanostructured materials showed high strength but poor results in terms of
ductility. In the low-ultrafine range (mean grain size between 100-500 nm) the three materials
showed an increase in the ductility with strain softening. Finally, when the average grain size was
close to 1 µm samples showed larger ductility and strain hardening.
Fracture Toughness Enhanced by Severe Plastic Deformation in Low Carbon Steel
Authors: Tanaka Masaki , Fujimoto Naoki , Yokote Tatsuo , Higashida Kenji
Published: March 2009

The enhancement of toughness at low temperatures in fine-grained low carbon steel was
studied, basing on the theory of crack-tip shielding due to dislocations. Low carbon steel was
subjected to an accumulative roll bonding (ARB) process for grain refining. The grain size
perpendicular to the normal direction was decreased to approximately 200nm after the ARB process.
The fracture toughness of low carbon steel with the ARB process was measured at 77K by four-point
bending, comparing with the fracture toughness of those without the ARB. It was found that the value
of fracture toughness at 77K was increased by grain refining due to the ARB process, indicating that
the ARB process enhances toughness at low temperatures and that the brittle-to-ductile transition
(BDT) temperature shifted to a lower temperature. Quasi-two-dimensional simulations of dislocation
dynamics, taking into account crack tip shielding due to dislocations, were performed to investigate
the effect of a dislocation source spacing along a crack front on the BDT. The simulation indicates
that the BDT temperature is decreased by decreasing the dislocation source spacing.
Microstructural Characterization of Low-Carbon Steel Processed by High Pressure Torsion and Annealing
Authors: Astafurova Elena G. , Dobatkin Sergey V. , Naydenkin Evgeny V. , Shagalina Svetlana V. , Zakharova Galina G.
Published: March 2009

Ultrafine grained low carbon steel processed by high pressure torsion (HPT) has been
investigated. Depending on initial state (ferritic-pearlitic state after normalization at 950°C, or
martensitic ones after quenching from 950°C and 1180°C), the evolution of the microstructure and
the mechanical properties was investigated after HPT and annealing at 400-600°C using
transmission electron microscopy and X-ray analysis. It has been shown that HPT of martensitic low
carbon steel provides a finer structure then that for ferritic-pearlitic initial state, and the initial
martensitic morphology and phase composition is strongly dependent on the temperature of
quenching. The initial structure was refined by HPT to 95nm in ferritic-pearlitic state and up to 65
and 50 nm in martensitic ones (after quenching from 950°C and 1180°C, respectively). Such
ultrafine grained structures demonstrate substantial mechanical properties and possess a high
thermal stability up to 500°C in all investigated states. Annealing for 1 h at 500°C results in grain
growth up to 860nm for ferritic-pearlitic initial state and 150-450 nm for martensitic ones.
Shear Deformation and Texture Evolution in Al Alloys Processed for One Pass by ECAP
Authors: Starink Marco J. , Wang Shun Cai , Qiao Xiao Guang , Gao Nong , Roven Hans Jørgen , Langdon Terence G.
Published: March 2009

The evolution of texture and deformation in the grains during one pass of equal-channel
angular pressing (ECAP) was examined for fine grained high strength and low strength Al alloys
and a coarse grained low strength Al alloy. The materials were analysed using electron back-scatter
diffraction (EBSD). The results are consistent with the materials responding to the intense
macroscopic shear stress by deformation of individual grains through movement of dislocations on
one or more of the slip crystallographic slip planes {hkl} that are favourably oriented, combined
with the rotation of grains to directions that bring main crystallographic slip planes parallel to the
macroscopic shear direction and crystallographic slip directions  parallel to two main shear
directions. Contrary to reports claiming up to 4 slip systems are activated, it was observed that only
the {111}<110> and {001}<110> shear systems are activated. Macroscopic shear deformation
occurs on two shear planes: the main shear plane (MSP), equivalent to the simple shear plane, and a
secondary shear plane which is perpendicular to the MSP.
UFG-Microstructures by Linear Flow Splitting
Authors: Müller Clemens , Bohn Tilman , Bruder Enrico , Groche Peter
Published: March 2009

Linear flow splitting is a new continuous cold forming process where the edge of a sheet
metal is formed into two flanges by splitting and supporting rolls. Thus the production of bifurcated
profiles from sheet metal without lamination of material becomes feasible. The production of such
structures takes place incrementally in a modified roll forming machine. Experimental investigateons
on a HSLA steel show, that even at a surface increase of the sheet edge of about 1800% no
cracks were nucleated in the profiles. EBSD measurements in the splitting centre reveal that similar
to other SPD processes UFG microstructures develop in the processing zone. Thus a steady state is
reached in the processing zone where increasing strain has no more (or little) influence on the
materials properties i.e. its deformability, as it is typical for SPD-processes. The formation of UFG
microstructures is considered to be a mandatory condition for the linear flow splitting process, as it
improves the formability of the material to the extremely high level required for this process. The
mechanical properties of profiles produced by linear flow splitting are characterised by large
gradients, depending on the local deformation and the resulting microstructure. Very high hardness
is measured at the former processing zone, i.e. the splitting centre and the flange surface, where
severe plastic deformation takes place and UFG microstructures are present. In direction to lower
deformation i.e. with increasing distance to the splitting ground or flange surface the hardness
decreases close to the level of the undeformed material. In the present paper the linear flow splitting
process is introduced and the microstructural development in the process zone is discussed on the
base of EBSD measurements on profiles of the steel ZStE 500. The repartition of mechanical
properties in a bifurcated profile is demonstrated by detailed hardness measurements.