Element Strategy Initiative International Advisory Council (ESIAC) 2019

Elements Strategy Initiativefor Structural Materials
ESISM

Director & Group Leader : Isao TANAKA (Kyoto University)
Group Leader : Haruyuki INUI (Kyoto University)
Group Leader : Nobuhiro TSUJI(Kyoto University)

1Strength is important(2012)Long suspension bridge(1889)

Airplane

Eiffel Tower
Fe: 7300 t

Tokyo SkyTree ®
Fe: 41000 t

Strength
100 MPa

Strength
500 MPa

M. Hirota et al. J. Jpn Weld Soc., 82 (2013) 21

Automobile

Reducing CO2 emissions
through lighter vehicles.

2Ductility is essential

Formability

Earthquake disaster@Kobe 1995
Shock absorption : Strength x Elongation(Ductility)

Essential for safe and secure society.

3Strength & Ductility of Materials

Stress (Strength)High strength Ceramics
BrittleFracture

MetalsPlastic Deformation

DuctileFracture

Polymers
DuctileFracture

Strain (Elongation, Ductility)4

Trade-off between strength & ductility

StrengthHigh strength
Ceramics
Targetmaterials
Martensitic Steel

MetalsHigh tension
Steel
Al Alloys

Ti alloys

IF steel

Polymers

Ductility5Dislocation mechanism in metals
Ductility increases
by enhanced movement andmultiplication of dislocations

Strength increases
by retarded movement andmultiplication of dislocations

solution
hardening

Dislocation

precipitation
hardening

Origin of the trade-off
relationship.

6

Bulk Nano-structured Materials (BNM)
Lower bound by conventional process
BNM(ultrafine grained materials

Commonly used
polycrystalline metals

BNM has recent focus due to discovery of unique properties.

7

Bulk Nano-structured Materials (BNM)

Strength (MPa)Four times enhancement of strength.
0.2μm

conventionalBNM

0.2μm

20μm

20μm

pure Allow carbon
steel
Aluminum stronger than steel !
N. Tsuji+ J. Nanoscience & Nanotechnology, 7 (2007), 3763.

8Bulk Nano-structured Materials (BNM)lowd=0.21μm carbon
steelpure Al

d=10μmTrue Stress /MPa

True Stress /MPad=0.27μm

d=13μmTrue Strain

True Strain
N. Tsuji+ J. Nanoscience & Nanotechnology, 7 (2007), 3763.

Still obeying the trade-off relationship.
We need to go beyond simple BNMsi.e., go beyond the dislocation theory.

9

ESISM Members
Nano & MicroAnalysis

Theory &Computation

Ikuhara PI
TEM/STEM

Tanaka GL

Inui GLFirst Principles
TheoryMicro pillaranalysis

AdvancedProcessing

Tsuji GL
Tsuzaki PI
Fatigue
Characterization

Bulk Nano
MetalsOhmura PI

Ogata PI
AtomicModelling

Sasaki PI
Mg Alloys

SteelsGoverningboard

10Research Topics
Topic 1. Plaston concept
Tsuji

Ogata

Inui

TanakaIkuharaTsuzakiOhmuraTopic 2. Realization of plaston induced plasticity materials
Topic 3. Plaston in brittle materials

Tsuji

TsuzakiOhmuraInui

IkuharaTopic 4. Atomic process of plastonby first principles and atomic simulations
Topic 5. Novel experimental techniques

Ogata

Tanakato analyze plaston processes
Tsuji

OhmuraInuiIkuhara

11

The plaston concept
Plaston: Atomic origin of plastic deformation in general.
Elastic
deformation

Collective
excitation of atoms

Plastic
deformation

Atomic frontof plastic
deformation

Nucleationof plastic
deformation

N.Tsuji, S.Ogata, H.Inui, I.Tanaka+, (2019).

Lattice defects left after
propagation of dislocations,formation of twins, martensites etc. 12

Compression test using μm-size single crystals
for quantitative & systematic single crystal mechanical property data

μm-size
single crystal

μm-sizeflat punch indenter(diamond)
μm-size single crystal
Compression Testμm-size pillar single crystal
Mg single crystal
dislocations

13

Atomic process of plaston : Simulation

Nucleation of dislocation loop (Ta)Dislocation nucleation
at grain boundary (Cu)
Activation Energy

Y.Sato, S.Ogata+, Int. J. Plast. 121 (2019) 280

14

Plaston process by advanced beam sources
in-situ neutron
diffraction

A. Shibata, N. Tsuji+, Scr. Mater. 165, (2019) 44

in-situ x-ray
diffraction

15

Newly discovered enhanced plasticity in BNM
MaterialPlaston mechanism
for enhanced
plasticity

Maximum
elongationin BNM

DiscoveryyearMg alloy

unusual dislocation+ deformation twin

0.26

2018

Cu alloy

deformation twin

0.43

2016

Austenitic
steelmartensitic
transformation

1.0

2016

High Mn
steel

deformation twin

0.55

2019

16

Achievements: SummaryIntellectual Merit Establishment of the new concept of plaston throughcollaboration of fundamental studies.
 Realization of new plaston induced plasticity materials.
Broader Impacts
 Development of new computational/experimental tools
useful for materials science in general.
 Transfer of ideas from fundamental research toindustry.
 Nurture of talented researchers.

17