Advanced Physical MetallurgyAdvanced Physical Metallurgy““Amorphous MaterialsAmorphous Materials””
EunEun SooSoo ParkPark
Office: 33-316 Telephone: 880-7221Email: [email protected] hours: by an appointment
2009 spring
06. 03. 2009
Recent BMGs with critical size ≥ 10 mm
A.L. Greer, E. Ma, MRS Bulletin, 2007; 32: 612.
Zr47Ti8Cu8Ni10Be27 Johnson (Caltech)Vitreloy
Pd60Cu30Ni10P20 Inoue (Tohoku Univ.)
Fe48Cr15Mo14Y2C15B6 Poon (Virginia Univ.)Amorphous steel
Ca65Mg15Zn20 15mm Kim (Yonsei Univ.)Ca60Mg25Ni20 13mmMg65Cu20Ag5Gd10 11mmMg65Cu7.5Ni7.5Zn5Ag5Gd5Y5 14mm
Limited Plasticity by shear softening and shear band
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Engi
neer
ing
Stre
ss (G
Pa)
0 2 4 6 8 10 12 14 16
Engineering Strain (%)
- low strength
- limited plasticity (0~2%) - catastrophic failure
20
200
Microscopically brittle fracture
Death of a material for structural applications
interrupt the localization of stress and deformation
• Prevent propagation of single shear band BMG matrix composites
• Multiple shear band formation
Plastic deformation in metallic glass•• No dislocation / No slip plane
• Inhomogeneously localized plastic flow in the shear band
Plastic deformation in metallic glasses
TEM Image of a shear band
~20 nm
Shear bands are ~20 nm in width
Size of heterogeneity
• Prevent propagation of single shear band
Micro- or nanometer scale heterogeneity
Elementary flow event in an metallic glasses
Size of heterogeneity
σ
σ
v>v*atomic volume
free volumefluctuation
ε0
Ω
defect volume shear strain
atomic scale heterogeneity
Probability )*
exp(fv
vA
average free volume
⎪⎪⎭
⎪⎪⎬
⎫
⎪⎪⎩
⎪⎪⎨
⎧
=f
VV
A 00 expηη
Flow governed by localized defect (~10 atoms) and creates defects
Phase separation in metallic glassesPhase separation in metallic glasses-- A New class of BMG composites A New class of BMG composites --
- Pd-Si-Ag alloy / two amorphous phase formation after heating just above TgChen and Turnbull, Acta Metall., 17, 1021 (1969)
- Zr-Ti-Cu-Ni-Be BMG / small angle neutron scatteringSchneider et al, Appl. Phys. Lett., 68, 493 (1996)
- Local composition change due to partitioning of alloying elementsMartin et al., Acta Mater., 52, 4427 (2004)
[1] Phase separation in solid state
- After heating just above Tg, two amorphous separation occurs, but crystallization occurs simultaneously.
immiscibility below the liquidus⇒ decomposition into metastable liquid
“Phase separation in glass” ed. by Mazurin and Porai-Koshits (1984)
Tc : critical temperature Tb : binodal curve Ts : spinodal curve
immiscibility above the liquidus⇒ decomposition into stable liquid
Metastable immiscibility
[2] Phase separation in liquid state
Stable immiscibility
-Kundig et al. , Acta Mater., 52, 2441 (2004)
Ni
LaZr
Al
Cu+4
+74
-239
-96 -32
-65-142
-38
-195
-161
Two liquids at high temperature (liquid decomposition)⇒ droplet structure
La-rich
Zr-rich
Previous studies
Y-rich
Nb-richY
Ni Nb-143
-161 +127
- N. Mattern et al. Scripta Mat. 53, (2005) 271
Ni58.5Nb20.25Y21.25
La27.5Zr27.5Al25Cu10Ni10
100nm
(Y56Al24Co20)65(Ti56Al24Co20)35
100nm100nm
(Y56Al24Co20) 25(Ti56Al24Co20)75 (Y56Al24Co20)50(Ti56Al24Co20)50
Droplet structure Droplet structureInterconnected structure
0 10 20 30 40 50 60 70 80 90 100400
600
800
1000
1200
1400
1600
Y56Al24Co20Ti56Al24Co20
T (K)
Ti
-38
-22
+15
-30
-28-19
Y
Al
Co
Previous studies
* Substitution of Nd with Zr in Nd-Co-Al system
-38
-44
-19
-20
-41
+10 Co Al
Nd
Zr
Nd-Co-Al , Zr-Co-AlPossibility of two phase !!!
• Sripta Mater. 56, 197 (2007)
Nd60Al10Co30 - 5mm
Zr55Al20Co25 - 3mm
Phase separation by adding elements having PEM
200 nm
SADP and Dark-field TEM image
Nd60Al10Co30
2.91 Å
Zr60Al10Co30
2.40 Å
Nd30Zr30Al10Co30
2.37 Å, 2.99 Å
TEM results for Nd30Zr30Al10Co30 alloy
300 350 400 450 500 550 600 650 700 750 800 850
ηmin = 3.17 *105
Temperature (K)
108
107
106
Nd60Al10Co30
Visc
osity
(Pa*
s)
105
300 350 400 450 500 550 600 650 700 750 800 850
Zr-rich
Temperature (K)
Nd30Zr30Al10Co30
ηmin = 6.56 *106
ηmin = 4.75 *106
108
106
107
Visc
osity
(Pa*
s)
Nd-rich
Measurement of viscosity using TMA
Selective partial devitrification (first SLR), followed by easy deformation of the amorphous/crystalline composite structure (second SLR) is possible for this alloy system.
-1.0 -0.5 0.0 0.5 1.0-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
⊥ Nd30Zr30Al10Co30
⎢⎢Nd30Zr30Al10Co30
10K 50K 100K 300K
Mag
netiz
atio
n (T
)
Magnetic field (T)
10K
0 50 100 150 200 250 300-2
0
2
4
6
8
10
12
14
16
Nd30Zr30Al10Co30⊥
Mag
netiz
atio
n (e
mu/
g)
temperature (K)
⎢⎢
Directional changes of magnetic property in two-phase metallic glass
Measurement of magnetic property using VSM
Gd30Ti25Al25Co20
100 nm
Gd30Ti25Al25Cu20
Gd-Cu
Ti
50 nm
Gd-Al
Ti-Co
Gd30Ti25Al25Ni20
100 nm
TiGd
0 10 20 30 40 50 60 70 80 90 100
1) Droplet structurein Gd-Ti-Al-(Co, Ni, Cu) alloy system
400
600
800
1000
1200
Composition (%)
Tem
p. (K
)
Ti
-38
-22
+15
-30
-28-19
Gd
Al
Co
* unpublished (2006)Phase separation
50 nm
Gd30Zr25Al25Co20
50 nm
Gd30Zr25Al25Cu20Gd30Zr25Al25Ni20
0 10 20 30 40 50 60 70 80 90 100400
600
800
1000
1200
Composition (%)
Tem
p. (K
)
Zr
-38
-22
+9
-44
-41-19
Gd
Al
Co
2) Interconnected structurein Gd-Zr-Al-(Co, Ni, Cu) alloy system
* unpublished (2006)
Phase separation
2 nm
① ②
①
②
Gd30Zr25Al25Co20 * unpublished (2008)
Nano scale (<3 mm) interconnected Phase separation
Enhancement of plasticity in BMG with atomic scale heterogeneity
atomic scale heterogeneity
a. Alloy design
1) quenched in quasi-nuclei in BMG
2) minor addition of elements havinglarge difference of enthalpy of mixing
-148
-181
+35
-142
-169
-38Zr Y
Cu
Al
Enhancement of plasticity in BMGs
100 nm
b. effect of atomic scale heterogeneity= multiple shear band formation
Phase separating metallic glasses
Unique properties
Are amorphous metals useful?Are amorphous metals useful?
High fracture strength over 5 GPa in Fe-based BMGsA.L. Greer, E. Ma, MRS Bulletin, 2007; 32: 612.
High strength of BMGs
- 8 0 8 16 24 32 40 48 56 64 7200.20.4
0.6
0.8
1.01.21.4
1.61.8 Conventional- 0.28 mm thick
Amorphous Fe80B11Si930 um thick
Magnetizing Field (H), A/m
Indu
ctio
n (B
), Te
sla
Magnetic cores
Transformers
0.1 1 10 100 100001000
Frequency , f [kHz]
1000
10000
100000
1000000P
erm
eabi
li ty
, [μ
]
Amorphous(Co- Based)
Permalloy(70 μm)
Nanocrystalline(VITROPERM)
Mn-Zn ferrite(Siferrit T38)
Low hysteresis loss
Frequency, f [kHz]
Perm
eabi
lity,
[μ]
www.metglas.com
Old uses: soft magnet
1) Micro-casting
TmeltingTg
Mol
ar V
olum
e, V
Liquid
Glass formation:continuous change
Crystal
Glass
Temperature, T
Crystallization:abrupt change
Near-net shape production
Cavity Die
Vacuum Chamber
Molten Alloy
InductionCoil
sleeve
Plunger
Die
Precision die casting
Precision Gears for Micro-motors
MRS BULLETIN 32 (2007)654.
Recently: processing metals as efficiently as plastics
2) Superplastic forming
400 500 600 700
Temperature (K) E
xoth
erm
ic (1
w/g
per
div
.)
Tg Tx
Am
orph
ous
Supe
rcoo
led
liqui
d
Stab
le li
quid
Crystalline Ts Tl
ΔTx
Tensile specimens following superplastic forming in supercooled liquid region
Recently: processing metals as efficiently as plastics
3) Micro-forming
Micro-forming of three-dimensional microstructures from thin-film metallic glass
Micro-cantilever Integrated conical spring linear actuator
Thickness: 5 μm
250 μm
50 μm
500
μm
Recently: processing metals as efficiently as plastics
Electronic Casings Medical DevicesSporting Goods
Defense ApplicationsIndustrial Coating Fine jewelry
Drill pipe, container etc. W-loaded composite BMGswww.liquidmetal.com
Commercialization of BMG products
TailormadeTailormade material designmaterial design
Ashby map
σ/E=10-4
10-3
10-2
10-1σ2/E=C
Elastomers
Polymers Foams
wood
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Strength σy (MPa)
Yo
un
gs
mo
du
lus,
E (
GP
a)
< Ashby map >
0.1 1 10 100 1000 100000.01
0.1
1
10
100
1000
Metallic glasses
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