Development of high toughness

Bulk metallic glass composite

with Transformation mediated 2nd phase

e-mail : hyunseok07@snu.ac.kr

2014.03.25. Current Status of Structural Materials

Seoul National University

Hyunseok Oh

Homepage : http://espark.snu.ac.kr

Contents

Development of “Work-hardenable” BMGCs with transformable 2nd

phases

Optimization of work-hardenability in BMGCs with transformable 2nd phases by controlling Vf and MS temp.

1) Fabrication of BMGCs with transformable 2nd phases

2) Evaluation of deformation mechanism in BMGCs

3) Hard ceramic, Soft crystalline, Transformation mediated

Comparison of Work-hardenability depending on 2nd Phases

4) Different martensitic transformation temperature

→ 2 different deformation behaviors of BMGCs depending on 2nd phases

work-softening vs work-hardening behavior → Self healing?

Brief introduction of BMGs and BMG matrix composites

Necessity of work hardenable bulk metallic glass composites

: Metallic Glasses Offer a Unique Combination of High Strength and High Elastic Limit

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Engin

eering S

tress

(G

Pa)

0 2 4 6 8 10 12 14 16

Engineering Strain (%)

“Conventional metal”

- low strength

“Amorphous metal”

- limited plasticity (0~2%)

- catastrophic failure

20㎛ 200㎛

Necessity of work hardenable bulk metallic glass composites

Possibility : Metallic Glasses has an intrinsic plasticity

Ceramic : Broken

Metallic glass : Weaken

Necessity of work hardenable bulk metallic glass composites

200 nm ~ 20 nm

clear boundary between undeformed matrix and shear bands

R

~ 20 nm

HRTEM image of a shear band

Shear deformed areas with the same composition & different density of free volume

Shear bands form by accumulation of defects during deformation.

Ref : Prof. Park

2) Transformation media

→ Work hardening

Douglas C. Hofmann, SCIENCE VOL 329 10 SEPTEMBER 2010

1) Ductile phase

→ Work softening

Necessity of work hardenable bulk metallic glass composites

BMG matrix CuZr B2 Transformation media

Yuan Wu, et al. Adv. Mater. 2010, 22, 2770–2773 [XRD pattern & Morphology of secondary phase before / after tensile test]

Necessity of work hardenable bulk metallic glass composites

Work-hardening behavior of BMGCs in tension

2) Transformation media

→ Work hardening

Douglas C. Hofmann, SCIENCE VOL 329 10 SEPTEMBER 2010

1) Ductile phase

→ Work softening

A

1. Size & Distribution

2. Volume fraction

3. Transformability: Martensitic transformation

Modulated Ex-situ Composite

To develop ultra tough BMGCs : Control the characteristics of 2nd phase

Necessity of work hardenable bulk metallic glass composites

1. Matrix Cu-based system

TiNi ~ Commercialized transformation media

with high performance 2. 2nd phase TiNiCu B2 phase

Preparation of Gas atomized powders

Preparation of metallic glass and SMA powders

-50 0 50 100 150

-0.4

-0.2

0.0

0.2

0.4

Heating

cooling

DSC trace

As -3.9°C

Af 17.2°C

Mf -21.0°C Ms -4.4°C

Temperature(°C)

ΔH=12.6J/g

ΔH=-12.6J/g

Secondary phase : TiNiCu powder B2 B19

200㎛

20 30 40 50 60 70 80

CC

C

Inte

nsi

ty(a

.u.)

2theta(degree)

C

10 20 30 40 50 60 70 80

0

2

4

6

8

10

12

14

16r

avg= 38.9 μm

Particle Size Distribution(Ti50Ni45Cu5)

fra

ctio

n(%

)

radius(um)

XRD

300 350 400 450 500 550 600

-20

-15

-10

-5

0

5

10

DSC

Tg 448°C Tx1 475°C

Temperature(°C)

20 30 40 50 60 70 80

Inte

ns

ity

(a.u

.)

2theta(degree)

XRD

0 20 40 600

2

4

6

8

10

12

14

16

18

fraction(%

)

radius(μm)

Particle Size Distribution(Cu54Ni6Ti18Zr22)

ravg=24.8μm

Matrix : Cu based metallic glass

200㎛

0 20 40 60 800

200

400

600

800

1000

Lo

ad

(uN

)

Displacement(nm)

2um conical tip, 5-2-5s

Conventional

metal

Superelastic property of TiNiCu 2nd phase

Nano-indentation

TiNi(B2)

B2 elastic

B2 B19(B19’)

B19(B19’)

Hysteresis loop : Superelasticity

B2 B19(B19’) reversible martensitic transformation 0

0

Strain

Str

ess

B2 elastic B2 B19’ B19(B19’)

Strain hardening

Pressure

POWDER

Powder

particle Electrical current

Joule heat

Discharge

Vacuum

chamber

Temperature : 440~470°C

Time : 15min

13mm disc, 7mm height

Pressing at Supercooled Liquid Region of mixed powders with high pressure (600MPa)

to consolidate the sample through viscous flow of metallic glass matrix.

Fabrication : Spark plasma sintering

Preparation of BMGC by Spark Plasma Sintering Method

20 30 40 50 60 70 80

30%

20%

10%

0%

C C

Inte

nsity(a

.u.)

2theta(degree)

C

500㎛

0%

500㎛

10%

500㎛

20%

500㎛

30%

XRD pattern SEM image

Ultrasonic measurement

Density(g/cm) v E(GPa) G(GPa) G/K

0% 7.90 0.360 80.6 29.6 0.21

10% 7.77 0.369 74.2 27.1 0.19

20% 7.67 0.374 70.6 25.7 0.18

30% 7.58 0.378 68.4 24.8 0.17

Fabrication : Spark plasma sintering

0.0 1.8 3.6 5.4 7.2 9.00

500

1000

1500

2000

(d)

x=30

(c)

x=20

(a)

x=0

Str

ess(M

Pa)

Strain(%)

Cu-based BMG + x% TiNiCu

(b)

x=10

1×10-4S-1 Uniaxial compression

1.93GPa

1.83GPa 1.86GPa

1.39GPa

2㎜

2㎜

4㎜

1. Large plasticity and Work hardening behavior

2. Fracture crack – propagate through interface of the 2nd phase and matrix

3. Multiple shear bands: initiation & propagation

0%

100μm 100μm

20%

Compression test: Large plasticity and work-hardening behavior

Cu-based BMGC with 20% TiNiCu

- Neutron source

diffractometer,

wave length=1.46Å

- Gauge volume:

2 x 2 x 2 mm3

(along the radial direction)

Deep penetration

depth (several

centimeters in most

materials)

Powerful tool for analyzing internal strain/phase in bulk samples

during deformation

-

Deformation Mechanism of BMGC with transformable 2nd phase

Neutron diffraction

36 37 38 39 40 41 42

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity

2theta(degree)

36 37 38 39 40 41 42

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity

2theta(degree)

36 37 38 39 40 41 42

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity

2theta(degree)

0 1 2 3 4

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Str

ess(M

Pa)

Strain(%)

B2

0MPa

1. M.T. is constrained by horizontal frame of MG matrix because of the imbalance of

Poisson’s ratio during M.T.(~0.5) with elastic loading of MG matrix(~0.33).

Work hardening of BMGCs

In-situ neutron diffraction measurement under compression

Work hardening

Cu-based BMGC with transformable 2nd phase (20% TiNiCu)

34 36 38 40 42 44

0

10

20

30

40

50

60

0kN

A

0kN

0 1 2 3 4

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Str

ess(M

Pa)

Strain(%) 1200MPa

In-situ neutron diffraction measurement under compression

Cu-based BMGC with transformable 2nd phase (20% TiNiCu)

Work hardening

1. M.T. is constrained by horizontal frame of MG matrix because of the imbalance of

Poisson’s ratio during M.T.(~0.5) with elastic loading of MG matrix(~0.33).

Work hardening of BMGCs

36 37 38 39 40 41 42

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity

2theta(degree)

36 37 38 39 40 41 42

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity

2theta(degree)

36 37 38 39 40 41 42

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity

2theta(degree)

B2

34 36 38 40 42 44

0

10

20

30

40

50

60

8.5

kN

A

8.5kN

36 37 38 39 40 41 42

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity

2theta(degree)0 1 2 3 4

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Str

ess(M

Pa

)

Strain(%) 1500MPa

In-situ neutron diffraction measurement under compression

Work hardening

Cu-based BMGC with transformable 2nd phase (20% TiNiCu)

2. M.T./slip deformation of 2nd phase are allowed to proceed with formation of shear

bands in the metallic glass matrix near yield strength.

Work hardening of BMGCs

36 37 38 39 40 41 42

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity

2theta(degree)

36 37 38 39 40 41 42

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity

2theta(degree)

36 37 38 39 40 41 42

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d In

ten

sity

2theta(degree)

B2

B19

34 36 38 40 42 44

-5

0

5

10

15

20

25

30

35

40

45

50

55

60

12

kN

A

12kN

0 1 2 3 4

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Str

ess(M

Pa)

Strain(%) 1800MPa

2. M.T./slip deformation of 2nd phase are allowed to proceed with formation of shear

bands in the metallic glass matrix near yield strength.

Work hardening of BMGCs

Work hardening

Cu-based BMGC with transformable 2nd phase (20% TiNiCu)

In-situ neutron diffraction measurement under compression

34 36 38 40 42 44

-5

0

5

10

15

20

25

30

35

40

45

50

55

60

13

kN

A

13kN

B2

B19

1. M.T. is constrained by horizontal frame of MG matrix because of the imbalance of

Poisson’s ratio during M.T.(~0.5) with elastic loading of MG matrix (~0.33).

.

Work-hardening of BMGCs with transformable 2nd phases

0 1 2 3 4 5

0

500

1000

1500

2000

Str

ess(M

Pa

)

Strain(%)

λ=2dsinθ , ε= d-d0

d

• Martensitic transformation

didn’t occur during elastic

loading of the composites.

• Lattice strain stopped

increasing at certain stress

level.

37.0 37.5 38.0 38.5 39.0 39.5 40.0 40.5 41.0

0.18

0.36

0.54

0.72

0.90

0

230

340

570

1220

1520

1670

1820

0un

1220re

1670re

2theta(degree)

Inte

nsity

App

lied

stre

ss(M

Pa)

B2

B19

B19’ B19

B19’

0.00 0.05 0.10 0.15

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Str

ess(M

Pa

)Lattice strain(%)

B2

B19,B19'

B2(Unloading)

In-situ neutron diffraction measurement under compression

B2

Str

es

s

Strain

2nd phase

Matrix

Str

es

s

“Strain hardening of 2nd phase contributes to work hardening behavior of BMGC.”

Strain hardening

Str

es

s

Strain

BMGMC

Work hardening

Mechanism of Work-hardening in BMGC with transformable 2nd phase

Bulk metallic glass composite

Hard ceramic, Soft crystalline, Transformation mediated

Comparison of Work-hardenability depending on 2nd Phases

Different martensitic transformation temperature

→ Applying deformation mechanisms to serrated flow

Comparison of Work-hardenability depending on 2nd Phases

H.C.

T.M.

S.C.

𝜎𝑝 = 𝜎 − 𝜎𝑦

𝜀𝑝 = 𝜀 − 𝜀𝑦 −𝜎𝑝

𝐸

• T.M. : Strain hardening

• H.C., S.C. : Strain softening

0 1 2 3 4 5 6 7 8 9 10 11 120

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

T

rue s

tress(M

Pa)

True strain(%)

1919 1817

1725

T.M. H.C. S.C.

Strain hardening(2nd) Work hardening

(T.M. > S.C. > H.C.) (T.M. > S.C. > H.C.)

Higher strain hardening of T.M., then larger work hardenability of BMGMCs

0.0 0.5 1.0 1.5

0

20

40

60

80

100

120

140

160

180

200

220

240

260

Pla

stic s

tre

ss(M

Pa

)

Plastic strain(%)

T.M.

H.C.

S.C.

Comparison of Work-hardenability depending on 2nd Phases

Mechanism of Work-hardening in BMGC with transformable 2nd phase

2.25 2.30 2.35 2.40 2.451944.2

1944.4

1944.6

1944.8

1945.0

1945.2

1945.4

1945.6

True strain(%)

2.45 2.50 2.55

1920

1925

1930

1935

1940

True strain(%)2.09402.09452.09502.09552.09602.09652.09702.09752.09802.0985

1925.5

1926.0

Tru

e s

tress(M

Pa)

True strain(%)

0 1 2 30

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

Tru

e s

tress(M

Pa)

True strain(%)

1919

H.C.

Yield UCS Fracture

0 1 2 3 4 5 6 70

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

Tru

e s

tre

ss(M

Pa

)

True strain(%)

4.70 4.75 4.80 4.85 4.901821.6

1821.8

1822.0

1822.2

1822.4

1822.6

1822.8

1823.0

True strain(%)1.960 1.962 1.964 1.966 1.968

1726.5

1727.0

1727.5

1728.0

1728.5

Tru

e s

tress(M

Pa)

True strain(%)

5.0 5.5 6.0

1812

1814

1816

1818

1820

1822

1824

True strain(%)

S.C.

1725

Yield UCS Fracture

0 1 2 3 4 5 60

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

Tru

e s

tre

ss(M

Pa

)

True strain(%)

3.90 3.95 4.00 4.05 4.101998.0

1998.2

1998.4

1998.6

1998.8

1999.0

1999.2

1999.4

True strain(%)

1.90 1.95 2.00 2.05 2.10 2.151810

1820

1830

1840

1850

1860

1870

Tru

e s

tress(M

Pa)

True strain(%)

4.30 4.35 4.40 4.45 4.50 4.55 4.60

1976

1980

1984

1988

1992

1996

True strain(%)

T.M.

1817

Yield UCS Fracture

Serrated flow

Δσ increases continuously

Δσ increases from 0 to 0.3~0.8 MPa and becomes saturated S.C. & T.M.

Why?

H.C.

Δσ~0.8

Ability of absorbing dissipated energy : T.M. > S.C. > H.C.

Δσ~10 Δσ~0 Δσ~0 Δσ~0.5 Δσ~0.5 Δσ~0 Δσ~0.3 Δσ~0.5

Str

ess

Composite

Matrix

2nd phase

Displacement

σy

Latt

ice s

train

O

Str

ess

Displacement

Latt

ice s

train

σy Composite

Matrix

2nd phase

σy

Composite

Matrix

2nd phase

Displacement

Latt

ice s

train

Str

ess

O O

Elastic Plastic Elastic Plastic Elastic Plastic ③ ① ② ④ ⑤ ③ ① ② ④ ⑤ ③ ① ② ④ ⑤

2nd phase – brittle fracture 2nd phase – strain hardening +martensitic transformation

Soft crystalline 2nd phase Hard ceramic 2nd phase Transformable 2nd phase

Metallic glass

SC

Metallic glass

SMA(M)

Metallic glass

HC

2nd phase – strain hardening

Str

ess

Composite

Matrix

2nd phase

Displacement

σy

Latt

ice s

train

O

Str

ess

Displacement

Latt

ice s

train

σy Composite

Matrix

2nd phase

σy

Composite

Matrix

2nd phase

Displacement

Latt

ice s

train

Str

ess

O O

Elastic Plastic Elastic Plastic Elastic Plastic ③ ① ② ④ ⑤ ③ ① ② ④ ⑤ ③ ① ② ④ ⑤

Soft crystalline 2nd phase Hard ceramic 2nd phase Transformable 2nd phase

Absorption mechanism of dissipated energy during shear banding

Hard ceramic None

Soft crystalline Strain hardening

Transformation mediated Martensitic transformation, Strain hardening

2nd phase – brittle fracture 2nd phase – strain hardening +martensitic transformation

2nd phase – strain hardening

-50 0 50 100-4

-3

-2

-1

0

1

2

3

4

Cooling

HeatingAs -2.4°C

Af 11.5°C

Mf -18.2°C Ms -2.7°C

Temperature(°C)

B (Ms= -3)

-50 0 50 100

-1

0

1

Cooling

HeatingAs -13.5°C Af 36.8°C

Mf -5.7°C Ms 32.4°C

Temperature(°C)

A (Ms= 32) #1 #2 #3

-10

0

10

20

30

Ms

Te

mp

era

ture

(oC

)

Yielding : Martensitic transformation

A (Ms= 32) B (Ms= -3)

C (Ms= -16)

Change the characteristics of 2nd phase

1. Different characteristic of Martensitic Transformation (A, B, C)

2. Same weight fraction (~volume fraction) of 2nd phase (20%)

Manipulation of Work-hardenability by Controlling 2nd Phases

-50 0 50 100

-1

0

1

Cooling

HeatingAs -25.2°C Af -4.4°C

Mf -38.5°C Ms -15.95°C

Temperature(°C)

C (Ms= -16)

-20 -10 0 10 20 30 40

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

3600

3800

4000

4200

4400

4600

4800

5000

Str

ess o

f m

art

en

sitic

tra

nsfo

rma

tio

n(M

Pa

)

Ms(degree)

C

B

A

Str

ess

A

B

C

Strain

Er(GPa) H(GPa) MT stress(GPa) Strain hardening

A 61.2±3.1 4.88±0.26 2.10±0.19

B 58.4±3.4 3.92±0.23 2.43±0.56

C 57.1±2.3 3.99±0.29 3.24±0.22

Strain hardening component

Measurement of martensitic transformation stress : Nano-indentation

Manipulation of Work-hardenability by Controlling 2nd Phases

𝜎𝑝 = 𝜎 − 𝜎𝑦

𝜀𝑝 = 𝜀 − 𝜀𝑦 −𝜎𝑝

𝐸

* “Work hardenability” ∝

“Strain hardenability after M.T.”

0 1 2 3 4 5 6 70

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

T

rue

str

ess(M

Pa

)

True strain(%)

1693

1817

1647

A B C

Ms(below R.T.) M.T. stress Strain hardening(2nd) Work hardening

(A > B > C // D) (A < B < C // D) (A > B > C // D) (A > B > C // D)

Higher Ms & Easier M.T. of 2nd phase, then larger work hardenability of BMGMCs

Manipulation of Work-hardenability by Controlling 2nd Phases

A

B

C

0.0 0.5 1.0 1.5

0

50

100

150

200

250

Pla

stic s

tress(M

Pa

)

Plastic strain(%)

1. Newly developed ex-situ BMGCs with transformable TiNiCu 2nd phase

exhibit large plasticity and superior work-hardening behavior.

2. Work hardening of BMGCs with transformable 2nd phase is from

delayed strain hardening of 2nd phase after matrix yielding, which

can be evaluated by in-situ neutron diffraction measurement

under compression test.

4. We can optimize work-hardenability of BMGCs by controlling

the fraction & martensitic transformability of 2nd phase in BMGC.

Conclusions

→ “Work hardenability” ∝ “Strain hardenability after M.T.”

3. The reason of superior work hardenability of BMGMCs with

transformation mediated 2nd phase is supposed to come from

higher performance of absorbing dissipated energy of shear

band by strain hardening and martensitic transformation.

Thank you for your kind attention