Nanometer-sized structural heterogeneity
CuZrAl BMGC
S. Pauly, S. Gorantla, G.Wang, U. Kühn and J. Eckert Nat. Mater., (2010), 9, 473-477
1
Nanometer-sized structural heterogeneity
CuZrAl-Co0.5 BMGC
Y. Wu, Y. H. Xiao, G. L. Chen, C. T. Liu and Z. P. Lu, Adv. Mater., (2010), 22, 2770-2773
2
Nanometer-sized structural heterogeneity
CuZrAl-Co0.5 BMGC
Y. Wu, Y. H. Xiao, G. L. Chen, C. T. Liu and Z. P. Lu, Adv. Mater., (2010), 22, 2770-2773
3
Martensitic transformation
Stress induced transformation
Schematic of the distortions transforming the CuZr B2 into the B19’ structure
Schryvers D, J. Phys. (1995), 5, 1047-1051
4
Nanometer-sized structural heterogeneity
CuZrAl BMGC
S. Pauly, S. Gorantla, G.Wang, U. Kühn and J. Eckert Nat. Mater., (2010), 9, 473-477
5
Martensitic transformation
Is there any size effect?
S. Pauly, S. Gorantla, G.Wang, U. Kühn and J. Eckert Nat. Mater., (2010), 9, 473-477
Y. Wu, Y. H. Xiao, G. L. Chen, C. T. Liu and Z. P. Lu, Adv. Mater., (2010), 22, 2770-2773
6
Shear Band on Ductile BMGs
The heterogeneities acted as obstacles during shear band
propagation, leaving a wavy shear band movement. This mechanism
was supposed to cause deflection and branching of shear bands in the
glassy matrix, resulting in a strain hardening effect.
Inoue, W. Zhang, T. Tsurui, A. R. Yavari, and A. L. Greer, Philos. Mag. Lett., (2005), 85, 221-229
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Strategy for improving plastic capability
Micrometer-sized structural heterogeneity
(a) Micrometer-sized ductile crystalline phase
(b) Micrometer-sized porosity
Extrinsic
toughening
Intrinsic
toughening
Nanometer-sized structural heterogeneity
(a) Nanocrystallization induced before deformation
(b) Nanocrystallization induced during deformation
(c) In-situ phase separation (or chemical inhomogeneity)
(d) Stress-induced twining
(e) Stress-induced Martensitic transformation
High Poisson’s ratio
Large amount of randomly distributed free volume
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Outline
a) Micrometer-sized structural
heterogeneity
b) Nanometer-sized structural
heterogeneity
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Micrometer-sized structural heterogeneity
SEM micrographs of (a) outer surface and (d) fracture surface
for the Mg-based BMGC. The inset in (b) shows the enlarged
view of the interface where a shear band travels into a particle;
the inset in (c) shows the shear bands propagation and branching
from deformed Nb particles
Pan DG, Zhang HF, Wang AM, Hu ZQ, Appl. Phys. Lett. 2006;89:261904.
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Micrometer-sized structural heterogeneity
Compressive stress-strain curves for the monolithic
Mg-based BMG and Nb-containing Mg-based BMGC
with volume fraction of 4% and 8%, respectively
Pan DG, Zhang HF, Wang AM, Hu ZQ, Appl. Phys. Lett. 2006;89:261904.
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Travels-Into or Branching-From
CuZrAl-Vx (x = 3, 5, 10)
Second phase: oversaturation
CuZrAl-Cox (x = 3, 5, 10)
Second phase: L1 + L2
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EDS results
Alloy
Element
(Cu47.5Zr47.5Al5)90V10
Cu
Zr
V
Al
Total
Average
(at%)
44.56
43.35
9.00
3.09
100.00
Dark Domain
(at%)
42.27
38.08
14.58
5.07
100.00
Bright Domain
(at%)
49.41
43.54
3.93
3.12
100.00
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EDS results
Alloy
Element
(Cu47.5Zr47.5Al5)90Co10
Cu
Zr
Co
Al
Total
Average
(at%)
44.17
42.78
10.09
2.96
100.00
Dark Domain
(at%)
55.73
32.29
1.04
10.94
100.00
Bright Domain
(at%)
35.58
41.43
20.72
2.27
100.00
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Travels-Into or Branching-From
sharp dendritic gray phases
rounded brighter phases
sharp dendritic gray phases
rounded brighter phases
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Stress concentration
Results of crack propagation
Griffith Crack
1/ 2
 a
 m = 2 o   = K t o
 t 
where
t = radius of curvature
o = applied stress
m = stress at crack tip
D. Hull and T. W. Clyne, An Introduction To Composite Materials, Cambridge, 1996
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Stress concentration
1/ 2
 a
 m = 2 o  
 t 
= K t o
Specimen
precipitated
phase (%)
(Cu47.5Zr47.5Al5)97V3
(Cu47.5Zr47.5Al5)95V5
(Cu47.5Zr47.5Al5)90V10
(Cu47.5Zr47.5Al5)97Co3
(Cu47.5Zr47.5Al5)95Co5
(Cu47.5Zr47.5Al5)90Co10
8
10
15
20
26
29
Stress
concentration
factor
6.60
8.26
8.62
3.32
3.77
3.82
D. Hull and T. W. Clyne, An Introduction To Composite Materials, Cambridge, 1996
17
Travels-Into or Branching-From
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Summary
Shear band is usually
nucleating/branching from the
stress concentration site
Shear band is usually traveling
into the second phase and slowing
down due to there is no obviously
stress concentration
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Fracture surface of CuZrAl-V10 sample
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Fracture surface of CuZrAl-Co10 sample
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Outline
a) Micrometer-sized structural
heterogeneity
b) Nanometer-sized structural
heterogeneity
22
SEM/BEI image
Cu47.5Zr47.5Al5
(Cu47.5Zr47.5Al5)99V1
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SEM/BEI image
Specimen
E (GPa)
y (GPa)
e (%)
p (%)
t (%)
Cu47.5Zr47.5Al5
87
1.8
2.0
2.7
4.7
(Cu47.5Zr47.5Al5)99V1
87
1.8
2.0
7.4
9.4
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TMA results
Variation of viscosity (measured by TMA) as a function temperature25
for the Cu47.5Zr47.5Al5 and (Cu47.5Zr47.5Al5)99V1 alloys.
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TMA results
Cu47.5Zr47.5Al5
(Cu47.5Zr47.5Al5)99V1
As cast
Specimen
Cu47.5Zr47.5Al5
(Cu47.5Zr47.5Al5)99V1
B2 ZrCu
<0.5 %
1 ± 0.3 %
After deformed
V-containing
phase
B2 ZrCu
0
0
1.5 ± 0.2 %
7.2 ± 1.0 %
V-containing
phase
26
0
0
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Mold Preparation
Different inlet
edge molds
(S mold)
(B mold)
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Reynolds number (Re)
Re
< 2300
2300 4000
> 4000
Cast by the S mold
Flow
Velocity Reynolds
Position
velocity
change
number
(m/s)
(m/s2)
(vL/)
Region 1, tank
0.03
20.7
916
Region 2, vena contraction
2.13
2107.0
7500
---Region 3, pipe of 4 mm
---Region 3, pipe of 3 mm
-Region 3, pipe of 2 mm
1.34
5953
flow status
laminar
laminar and
turbulent
turbulent
Cast by the B mold
Flow
Velocity Reynolds
velocity
change
number
(m/s)
(m/s2)
(vL/)
0.02
0.1
274
---0.20
6.0
1741
0.35
30.3
2322
-0.78
3483
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Effect of Vena Contraction
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Effect of Vena Contraction
Vena Contraction
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Size Effect of Martensitic transformation
Strain Hardening!
Mold
type
S mold
B mold
CuZrAl
E
y
(GPa) (GPa)
87
1.8
84
1.7
t
~5%
17%
Mold
type
S mold
B mold
CuZrAl-Co
E
y
(GPa) (GPa)
85
1.7
84
1.7
t
20%
23%
31
Size Effect of Martensitic transformation
(S mold)
Mold
E
type
(GPa)
S mold
87
B mold
84
(B mold)
Cu47.5Zr47.5Al5
y
t
(GPa)
1.8
~5%
1.7
17%
AC B2 DF B19’
d (nm) d (nm)
~5 (B2)
~3
~20
~10
Martensitic
transformation
and twin
32
Summary
CuZrAl (B mold)
CuZrAl (S. Pauly)
CuZrAl-Co0.5 (Y. Wu)
CuZrAl
(S mold)
CuZrAl-V1
CuZrAl
(B mold)
CuZrAl
(S. Pauly)
CuZrAl-Co0.5
(Y. Wu)
Martensitic
transformation
or Twinning
X
X
O
(M and T)
O
(T)
O
(M)
Size of B2 CuZr
phase(DF)(nm)
~5
~10
15-20
40-50
80
Critical size
Y. Wu, Y. H. Xiao, G. L. Chen, C. T. Liu and Z. P. Lu, Adv. Mater., (2010), 22, 2770-2773
S. Pauly, S. Gorantla, G.Wang, U. Kühn and J. Eckert, Nature Mater., (2010), 9, 473-477
33
Thank You
「蛋黃哥」的圖片搜尋結果
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