Comportement mécanique des verres métalliques massifs - Effet dune cristallisation partielle Sous...
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Transcript of Comportement mécanique des verres métalliques massifs - Effet dune cristallisation partielle Sous...
Comportement mécanique des verres métalliques massifs
-Effet d’une cristallisation partielle
Sous la direction de :
Jean-Jacques Blandin
Sébastien Gravier
Mechanical behavior of bulk metallic glasses-
Impact of the partial crystallization
Supervised by :
Jean-Jacques Blandin
Sébastien Gravier
3
Cooling a metal Crystallization
Temperature
Vol
ume
Tm
Liquid stateSolid state
Conventional solidification
4Production of a metallic glass
Cooling a metal Crystallization
Temperature
Vol
ume
Tm
Liquid stateSupercooled Liquid Region(SLR)
To avoid crystallization Rapid cooling
Tg
Glassy state
Metallic glass
Limited size !
More complex compositions to have Bulk metallic glasses
5Aim of the work
Temperature
Vo
lum
eSupercooled Liquid Region
Glassy state Tg
Crystallization
Effects ?
Room temperature : RT(T << Tg)
High temperature : HT(T>Tg)
Tg Nanocrystals
100 nm
brittleness large strain
5 mm
6
Aim: effect of crystallisation on mechanical properties at RT and HT
Room Temperature High Temperature
compression
DMAnanoindentation
compression
How the crystallisation modify the plasticity characteristics ?
How the crystals contribute to change the mechanical response ?
(rheology, elementary mechanism of deformation, reinforcement...)
Validation for the amorphous alloy
Mechanicalcharacterisation
methods
7
Validation for the amorphous alloy
Aim: effect of crystallisation on mechanical properties at RT and HT
Room Temperature High Temperature
compression
DMAnanoindentation
compression
Microstructural characterisation
DSC TEMXRD
Crystal volume fraction ?
How the crystallisation modify the plasticity characteristics ?
How the crystals contribute to change the mechanical response ?
(rheology, elementary mechanism of deformation, reinforcement...)
Mechanicalcharacterisation
methods
8
Aim: effect of crystallisation on mechanical properties at RT and HT
High Temperature
DMA
compression
Microstructural characterisation
DSC TEMXRD
Crystal volume fraction ?
How the crystallisation modify the plasticity characteristics ?
How the crystals contribute to change the mechanical response ?
(rheology, elementary mechanism of deformation, reinforcement...)
Validation for the amorphous alloy
compression
nanoindentation
Mechanicalcharacterisation
methods
Room Temperature
9Room temperature
Elements Zr Ti Cu Ni BeAtomic % 41.2 13.8 12.5 10 22.5
BMG studied in this thesis
Vit1 (Tg = 365 °C )
10
E ≈ corresponding crystalline alloys
+
f = 1830 MPa ( 1 %)
elast ≈ 0.02
Macroscopic brittleness
Compression tests at room temperature on a BMG
Macroscopic brittleness but local plasticity
Ef
Room temperature
elast
BMG studied in this thesis
Vit1 (Tg = 365 °C )Elements Zr Ti Cu Ni BeAtomic % 41.2 13.8 12.5 10 22.5
20 µm20 µm
Microscopic plasticity
Fracture surface
11
0
50
100
150
200
250
300
350
0 500 1000 1500
Depth "h" (nm)
Lo
ad "
L"
(mN
)
Nanoindentation loading and unloading curves
Room temperature
L
h
Loading curve : L = C h2
Unloading curve:
( Irreversible Work ratio ) RW = Wirr / Wtot
Collaboration: L. Charleux ( INP-Grenoble )
12
Loading curve : L = C h2
Unloading curve:
( Irreversible Work ratio ) RW = Wirr / Wtot
0
50
100
150
200
250
300
350
0 500 1000 1500
Depth "h" (nm)
Lo
ad "
L"
(mN
)
Nanoindentation loading and unloading curves
Wtot
Wirr
Room temperature
> Silica Glass ≈ 40 %
< Aluminium ≈ 100 %
Suggest many dissipative events !
= 67 %
13
0
50
100
150
200
250
300
350
0 500 1000 1500
Depth "h" (nm)
Lo
ad "
L"
(mN
)
Nanoindentation loading and unloading curves
Wtot
Wirr
5 µm
21 2d
eqc
SEE
A
Materials Science and Engineering A (2006)
Sd
Room temperatureLoading curve :
L = C h2
Unloading curve:
( Irreversible Work ratio ) RW = Wirr / Wtot
> Silica Glass ≈ 40 %
< Aluminium ≈ 100 %
Suggest many dissipative events !
= 67 %
AFM measurements : reduced Young modulus : Eeq
14
0.6
0.61
0.62
0.63
0.64
0.65
0.66
0.67
0.68
0.69
0.7
1.1 1.15 1.2 1.25 1.3
C/Eeq
Rw
Von Mises
Amorphous
Room temperature
In this plane
Von Mises criterion : y
Line in this plane
Plasticity map extracted from nanoindentation curves: gives plastic properties independently of elastic behavior
15
0.6
0.61
0.62
0.63
0.64
0.65
0.66
0.67
0.68
0.69
0.7
1.1 1.15 1.2 1.25 1.3
C/Eeq
Rw
Von Mises
Amorphous
> 0
< 0
Room temperature
Drucker Pragger criterion :
y and α (pressure sensitivity)
Upper part : > 0
Lower part : < 0
In this plane
Von Mises criterion : y
Line in this plane
Plasticity map extracted from nanoindentation curves: gives plastic properties independently of elastic behavior
16
0.6
0.61
0.62
0.63
0.64
0.65
0.66
0.67
0.68
0.69
0.7
1.1 1.15 1.2 1.25 1.3
C/Eeq
Rw
Von Mises
Amorphous
> 0
< 0
Plasticity map extracted from nanoindentation curves: gives plastic properties independently of elastic behavior
Both values of y in agreement with compression
in agreement with
Vaidyanathan 2001
Patnaik 2004Nanoindentation: Fruitful technique to study deformation at room temperature (in particular pressure sensitivity)
Room temperature
Drucker Pragger criterion :
y and α (pressure sensitivity)
Upper part : > 0
Lower part : < 0
In this plane
Von Mises criterion : y
Line in this plane
17
Aim: effect of crystallisation on mechanical properties at RT and HT
Room Temperature
compression
nanoindentation
Microstructural characterisation
DSC TEMXRD
Crystal volume fraction ?
How the crystallisation modify the plasticity characteristics ?
How the crystals contribute to change the mechanical response ?
(rheology, elementary mechanism of deformation, reinforcement...)
Validation for the amorphous alloy
High Temperature
DMA
compressionMechanicalcharacterisation
methods
18
1,E+08
1,E+09
1,E+10
1,E+11
1,E+12
1,E+13
1,E-05 1,E-04 1,E-03 1,E-02 1,E-01
Strain rate (s-1)
Vis
cosi
ty (
Pa.
s)
Room temperature fracture stress
T decreases
Tg - 10 °C
Tg + 40 °C
Viscosity as function of strain rate / compression
0
50
100
150
200
250
300
350
0 0.2 0.4 0.6 0.8Strain
Str
ess
(MP
a)
5.10-3 s-1
5.10-4 s-15.10-4 s-1
T = Tg + 10 °C
Large strains
3
High temperature
Compression tests at Tg + 10 °C, various strain rates
Viscoplastic deformation in
steady state
19
1,E+08
1,E+09
1,E+10
1,E+11
1,E+12
1,E+13
1,E-05 1,E-04 1,E-03 1,E-02 1,E-01
Strain rate (s-1)
Vis
cosi
ty (
Pa.
s)
Room temperature fracture stress
T decreases
Tg - 10 °C
Tg + 40 °C
Confirmation of usual deformation behaviour in SLR
Newtonian regimeHigh temperature / low strain rate
Non Newtonian regimeLow temperature / high strain rate
Viscosity as function of strain rate / compression
Newtonian
Non Newtonian
High temperature
20
0.01
0.1
1
10
1.E+05 1.E+06 1.E+07 1.E+08 1.E+09 1.E+10N
/
N
Tg - 10°C
Tg + 50°C
Creation of a unique master curve for various temperatures
High temperature
effect of T : just translation
0 exp( )N
Q
RT Suppose:
Q = 440 kJ/mol
Complex multiatomic mechanism (activation volume ≈ 20 atoms)in large strain …
(strong temperature sensitivity)
Sensitivity to temperature:
Newtonian viscosity
Ability to draw a master curve:
Sensibility of viscosity to strain rate independent of temperature
21
0.01
0.1
1
10
1.E+05 1.E+06 1.E+07 1.E+08 1.E+09 1.E+10N
/
N
Tg - 10°C
Tg + 50°C
Creation of a unique master curve for various temperatures
0 exp( )N
Q
RT Suppose:
Q = 440 kJ/mol
Complex multiatomic mechanism (activation volume ≈ 20 atoms)in large strain …
High temperature
Data obtained in steady state (large strain)
Is there a minimum strain to measure these features ?
effect of T : just translation
Sensitivity to temperature:
Newtonian viscosity
Ability to draw a master curve:
Sensibility of viscosity to strain rate independent of temperature
22
Dynamic Mechanical Analysis (DMA) : Sinusoidal small strain tests
0
0,05
0,1
0,15
0,2
0,25
0,3
0,01 0,1 1 10f (Hz)
G"/
Gu
Frequency scans at various fixed temperatures
T
High temperature
Collaboration: Jean–Marc Pelletier, INSA - Lyon
Dissipative part of the deformation :
Construction of a master curve
0
0,05
0,1
0,15
0,2
0,25
0,3
0,0001 0,01 1 100"Translated" f (Hz)
G"/
Gu
Phase difference between applied stress and strain
"G
Gu
23
Dynamic Mechanical Analysis (DMA) : Sinusoidal small strain tests
0
0,05
0,1
0,15
0,2
0,25
0,3
0,01 0,1 1 10f (Hz)
G"/
Gu
Frequency scans at various fixed temperatures
T
High temperature
Collaboration: Jean–Marc Pelletier GEMPPM, INSA
Dissipative part of the deformation :
Construction of a master curve
0
0,05
0,1
0,15
0,2
0,25
0,3
0,0001 0,01 1 100"Translated" f (Hz)
G"/
Gu
"G
Gu
Elementary mechanism of deformation independent of TApparent activation energy ~ 400-450 kJ/mol
Similar mechanical behaviours in the investigated conditions(T and both small and large strains)
DMA + Compression : Fruitful techniques to study deformation at HT in a large strain interval
Phase difference between applied stress and strain
24
Validation for the amorphous alloy
Aim: effect of crystallisation on mechanical properties at RT and HT
Room Temperature High Temperature
compression
DMAnanoindentation
compression
How the crystallisation modify the plasticity characteristics ?
How the crystals contribute to change the mechanical response ?
(rheology, elementary mechanism of deformation, reinforcement...)
Microstructural characterisation
DSC TEMXRD
Crystal volume fraction ?
Mechanicalcharacterisation
methods
25
0 20 40 60 80 100
Annealing time (min.)
En
do
the
rmic
he
at
flo
w (
a.u
.)_
Crystallization / Microstructure
Isothermal annealing DSC at Tg + 50 °CAmorphous : transformed fraction Ft = 0%
100 nm100 nm
~ 30 nmFt = 10 %
10 min.
100 nm100 nm
Φ ~ 35 nmFt = 60 %
30 min.
100 nm100 nm
Φ ~ 30 nmFt = 45 %
20 min.
100 nm100 nm
Crystallite average size Φ ~ 35 nmFt ≈ 100 %
60 min.
100 nm100 nm
Φ ~ 35 nmFt = 80 %
45 min.
Various heat treatments
26
0 20 40 60 80 100
Annealing time (min.)
En
do
the
rmic
he
at
flo
w (
a.u
.)_
Crystallization / Microstructure
Isothermal annealing DSC at Tg + 50 °CAmorphous : transformed fraction Ft = 0%
100 nm100 nm
~ 30 nmFt = 10 %
10 min.
100 nm100 nm
Φ ~ 35 nmFt = 60 %
30 min.
100 nm100 nm
Φ ~ 30 nmFt = 45 %
20 min.
100 nm100 nm
Crystallite average size Φ ~ 35 nmFt ≈ 100 %
60 min.
100 nm100 nm
Φ ~ 35 nmFt = 80 %
45 min.
Various heat treatments
Spherical crystallites + constant average size
27Crystallization / volume fraction
Direct measurements through TEM imaging
100 nm
100 nmd
100 nmd
100 nm
Dark field observation Thickness measurement
Bright field observation
Crystal superposition and lack of contrast in bright field
Dark field measurements of volume fraction
Collaboration: P. Donnadieu (LTPCM – INPG)
28
To calculate the real volumefraction we need to have onlyone crystal type :
Crystallite sizeCrystallite nature
Crystallization / volume fraction
annealing time ≤ 30 min.
Direct measurements through TEM imaging
100 nm
100 nmd
100 nmd
100 nm
Dark field observation Thickness measurement
Bright field observation
Crystal superposition and lack of contrast in bright field
Dark field measurements of volume fraction
0 min. 10 min. 20 min. 30 min.
Fv (%) 0 4 1 17 4 26 5
TEM volume fraction of crystals depending on annealing time at Tg + 50 °C
Collaboration: P. Donnadieu (LTPCM – INPG)
29Crystallization / volume fraction
Crystals randomly oriented
Density constant
(d / d < 1 %)
Direct measurements through XRD analysis
0,751,251,752,252,75dhkl (A)
Cou
nts
Amorphe
10mn
45mn
30mn
60mn
20mn
XRD curves for the various samples
30
20 30 40 50 60 70 80
angle (2q)
Co
un
ts
Separation of the amorphous and crystalline contributions.
Amorphous
60 min.
Volume fraction of crystals
Crystallization / volume fraction
Crystals randomly oriented
Density constant
(d / d < 1 %)
Direct measurements through XRD analysis
Crystallized part
Amorphous part
31
Amorphous 10 min. 20 min. 30 min.
Volume fraction
(%)
TEM 0 4 1 17 4 26 5
XRD 0 7 3 17 3 27 3
Equivalent values with the two methods :
Validation of the measurement methodsXRD analysis is an accurate way to measure Volume fraction of crystals (even for small crystallites)
Validation of the method
Crystallization / volume fraction
32
Amorphous 10 min. 20 min. 30 min. 45 min. 60 min.
Volume fraction
(%)
TEM 0 4 1 17 4 26 5 ? ?
XRD 0 7 3 17 3 27 3 32 3 45 5
Validation of the method
Crystallization / volume fraction
Equivalent values with the two methods :
Validation of the measurement methodsXRD analysis is an accurate way to measure Volume fraction of crystals (even for small crystallites)
33
Amorphous 10 min. 20 min. 30 min. 45 min. 60 min.
Volume fraction
(%)
TEM 0 4 1 17 4 26 5 ? ?
XRD 0 7 3 17 3 27 3 32 3 45 5
DSC Ft (%) 0 10 45 60 80 100
Validation of the method
Large difference with predicted DSC transformed fraction(while sometimes used as crystalline fraction…)
Crystallization / volume fraction
Equivalent values with the two methods :
Validation of the measurement methodsXRD analysis is an accurate way to measure Volume fraction of crystals (even for small crystallites)
34
Validation for the amorphous alloy
Aim: effect of crystallisation on mechanical properties at RT and HT
High Temperature
compression
DMAnanoindentation
compression
Microstructural characterisation
DSC TEMXRD
How the crystals contribute to change the mechanical response ?
(rheology, elementary mechanism of deformation, reinforcement...)
Room Temperature
How the crystallisation modify the plasticity characteristics ?
Mechanicalcharacterisation
methods
Crystal volume fraction : OK
35
Validation for the amorphous alloy
Aim: effect of crystallisation on mechanical properties at RT and HT
High Temperature
compression
DMAnanoindentation
compression
Microstructural characterisation
DSC TEMXRD
Crystal volume fraction : OK
How the crystals contribute to change the mechanical response ?
(rheology, elementary mechanism of deformation, reinforcement...)
Room Temperature
How the crystallisation modify the plasticity characteristics ?
Mechanicalcharacterisation
methods
36Effect of crystallization / room temperature
Fracture stress increases slightly and then falls !
Journal of Alloys and Compounds (2006)
Fracture stress as a function of annealing time
Nanoindentation is even more interesting to study plasticity
Change in fracture mechanism :
Fragmentation rather than shear fracture for Fv > 30 %
500
700
900
1100
1300
1500
1700
1900
2100
0 10 20 30 40 50 60
Fv (%)
Fra
ctu
re s
tres
s (M
Pa)
_
37
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.5 1 1.5
C/Eeq
Rw
Effect of crystallization / room temperature
Journal of Materials Research (2007)
Plasticity map extracted from nanoindentation curves
Al
Silica
Amorphous
38
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.5 1 1.5
C/Eeq
Rw
Effect of crystallization / room temperature
Journal of Materials Research (2007)
Plasticity map extracted from nanoindentation curves
Al
Silica
At room temperature:
Effect on fracture rather than on deformation mechanisms
Effect of crystallization
(Fv < 0.5)
Very limited variations of Rw and C/Eeq
Still sensitive to pressure
39
Validation for the amorphous alloy
Aim: effect of crystallisation on mechanical properties at RT and HT
Room Temperature
compression
DMAnanoindentation
compression
Microstructural characterisation
DSC TEMXRD
Crystal volume fraction : OK
How the crystallisation modify the plasticity characteristics ?
High Temperature
How the crystals contribute to change the mechanical response ?
(rheology, elementary mechanism of deformation, reinforcement...)
Mechanicalcharacterisation
methods
40Effect of crystallization / high temperature
Two main effects of crystallization
Increase of viscosity
Promotion of non Newtonian behaviour
The reinforcement for a given temperature depends on strain rate
Viscosity depending on strain rate
Deformation ability is maintained up to large Fv
1,E+09
1,E+10
1,E+11
1,E+12
1,E+13
1,E-05 1,E-04 1,E-03 1,E-02Strain rate (s-1)
Vis
cosi
ty (
Pa.
s)
amorphous
Fv = 7 %
T = Tg + 20°C
Increase of the viscosity
decrease oflim itFv = 32 %
Fv = 27 %
Fv = 17 %
Fv = 45 % : brittle behaviour
41Effect of crystallization / high temperature
Similar mechanical behaviours in the investigated conditions(Fv, T and large strains)
Viscosity curves : all temperatures and annealing times / translated along the two axes
"Translated" strain rate
"Tra
nsl
ated
" V
isco
sity
~ 25 compression tests Still ability to draw master curves
Strain rate dependence of viscosity is the same for the various temperatures and Fv
Effect of T : still just translation
42Effect of crystallization / high temperature
DMA curves : all temperatures and annealing times / translated along the two axis
0
0,05
0,1
0,15
0,2
0,25
0,01 1 100 10000 1000000frequency "translated" (Hz)
G"
"tra
nsl
ated
"
THERMEC (2006)
~ 200 curves
Again able to draw master curves
Same elementary mechanism of deformation for the various temperatures and Fv
43Effect of crystallization / high temperature
Reinforcement depends on strain rate…
Comparison performed in Newtonian regime
( )VF
NAmorphousN
R Fv
Similar mechanical behaviours in the investigated conditions(Fv, T and both small and large strains)
Prediction of the reinforcement factor ( ) ?VF
Amorphous
The amorphous matrix seems responsible for the deformation
44
1
10
100
1000
0 10 20 30 40 50 60Fv (%)
Rei
nfo
rcem
ent
fact
or
: R
Effect of crystallization / high temperature / reinforcement
Prediction of R from mechanical models ?
Hard sphere dispersion in a viscous media : Krieger model
T = Tg + 30 °C( )VF
NAmorphousN
R Fv
Reinforcement factor for various Fv (less than 30 %)
45
1
10
100
1000
0 10 20 30 40 50 60Fv (%)
Rei
nfo
rcem
ent
fact
or
: R
Effect of crystallization / high temperature / reinforcement
Underestimate the reinforcement !!
Prediction of R from mechanical models ?
Hard sphere dispersion in a viscous media : Krieger model
T = Tg + 30 °C
Krieger model
( )VF
NAmorphousN
R Fv
Reinforcement factor for various Fv (less than 30 %)
46
1
10
100
1000
0 10 20 30 40 50 60Fv (%)
Rei
nfo
rcem
ent
fact
or
: R
Effect of crystallization / high temperature / reinforcement
Reinforcement factor for various Fv (less than 30 %) and temperatures
Underestimate the reinforcement !!
T decreases
Tg
Tg + 30°C
Reinforcement depends on strain rate and temperature(simple mechanical models are not adapted)
Prediction of R from mechanical models ?
Hard sphere dispersion in a viscous media : Krieger model
Various T
Krieger model
( )VF
NAmorphousN
R Fv
47
ISMANAM (2006)
0 exp( )N
Q
RT
Still able to use an Arrhenius law
Activation energies in SLR measured by two ways
0
100
200
300
400
500
0 10 20 30 40 50 60
Fv (%)
Ap
par
ent
acti
vati
on
en
erg
y (k
J/m
ol)
_
compressionDMA
Effect of crystallization / high temperature / reinforcement
Temperature
New
ton
ian
vis
cosi
ty
Glass
Partially crystallized
48
0 exp( )N
Q
RT
Still able to use an Arrhenius law
ISMANAM (2006)
Activation energies in SLR measured by two ways
Reinforcement increases with temperature because:Decrease of viscosity is less rapid when crystals are present
0
100
200
300
400
500
0 10 20 30 40 50 60
Fv (%)
Ap
par
ent
acti
vati
on
en
erg
y (k
J/m
ol)
_
compressionDMA
Effect of crystallization / high temperature / reinforcement
Temperature
New
ton
ian
vis
cosi
ty
Glass
Partially crystallized
49Effect of crystallization / high temperature / activation energies
• Direct change in composition of the residual glass ?
Three possible reasons to explain the decrease of activation energy
ISMANAM (2006)
NO( ∆ Tg < 4 °C )
NO( TEM observationsafter deformation > 1.5 )
• Direct contribution of crystal deformation ?
50Effect of crystallization / high temperature / activation energies
• Direct change in composition of the residual glass ?
• Direct contribution of crystal deformation ?
• Influence of the coupling between matrix and crystals ?
Three possible reasons to explain the decrease of activation energy
Matrix layer perturbed by the proximity of crystals
Small “flow channels” between crystallites
d
Modification of matrix activation energy at crystal neighborhood
51Effect of crystallization / high temperature / activation energies
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50Fv (%)
Rat
io "
per
turb
ated
am
orp
ho
us
/ to
tal r
emai
nin
g a
mo
rph
ou
s"
1 nm
3 nm
5 nm
Fraction of amorphous matrix perturbed because of proximity of crystals
Effect of various interface thickness
coupling between matrix and crystals (crystal size ≈ 30 nm) ?
52Effect of crystallization / high temperature / activation energies
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50Fv (%)
Rat
io "
per
turb
ated
am
orp
ho
us
/ to
tal r
emai
nin
g a
mo
rph
ou
s"
Fraction of amorphous matrix perturbed because of proximity of crystals
Nanometer crystallites Large fraction of the remaining amorphous matrix can be disturbed by crystal proximity
coupling between matrix and crystals (crystal size = 30 nm) ?
1 nm
3 nm
5 nm
Distance between crystallites effect
Visualization of the small distances between
crystals : Fv = 30 %
30 nm
Effect of various interface thickness
53
Validation of new methods
- compression / nanoindentation
fracture vs. plasticity calculation of both the pressure sensitivity and the yield stress
- compression / DMA
large strain interval deformation mechanism at small strains vs. large strain mechanism
- TEM / XRD
Measurements of the volume fraction of crystals
Main conclusions
54Main conclusions
Open questions on the effect of crystallization
- At room temperature: Does the crystals modify the plasticity characteristics ?
Modify the fracture (fragmentation for Fv > 30 %) Limited modification of the plastic mechanism
Small variation of RwStill a pressure sensitivity
- At high temperature: How the crystals contribute to change the mechanical response ?
Deformation mechanism seems similar whatever Fv (< 50 %), the strain or the temperature Promotion of non Newtonian behavior Reinforcement effect depends on temperature
55Perspectives / scientific
Modelling the high temperature deformation
Similarity between deformation mechanisms for small strain and large strain
Interest of the definition of the elementary mechanism of deformation
56Perspectives / scientific
Modelling the high temperature deformation
Similarity between deformation mechanisms for small strain and large strain
Need to go from elementary deformation to macroscopic deformation
Flow defect concentration
Interest of the definition of the elementary mechanism of deformation
Elementary shear mechanism of Argon
Flow defect
57Perspectives / scientific
Study of the size effect of nanocrystals
One comparison point already achieved:
Fv = 16% + Mean crystallite size = 7 nm
Fv = 17% + Mean crystallite size = 30 nm
and
No differences observed … … up to now !!
58Perspectives / technological
Interest of bulk metallic glasses / metallic alloys composites
Patent in progress
10 mm
Advanced Engineering Materials (2006)
1 mm
Al-alloy
Vit1
Interesting mechanical properties…
Fracture stress + Plasticity + High interface shear stress
Co-deformed multimaterials designed thanks to the deformation ability of the glass in the SLR
Resistance of metallic glass + ductility of metallic alloy
Push out tests
1 mm
Al-alloy
Vit1
59
Merci à …
Ludovic CharleuxBéatrice Doisneau-CottigniesPatricia DonnadieuMarc FivelAlexandre MussiJean-Marc PelletierLuc SalvoJean-Louis SoubeyrouxMichel SueryAndré SulpiceMarc VerdierQing Wang
… pour leurs contributions à ce travail
60
61
62Conclusion and ….perspectives
Crystallites size effect (heat treatments at other temperatures)
Room temperatureYoung modulus
High temperatureModel of deformation based on the Argon model
Effect of the high temperature deformation on the crystallization
Point not aborded
Materials Science and Engineering A (2006)
63
Link between localized deformation and homogeneous flow ?
Characterization of the localized deformation
Influence of a temperature increase
Transition with homogeneous flow0
500
1000
1500
2000
0 0,05 0,1 0,15
Strain
Str
es
s (M
Pa)
Compression test at room temperature:Zr based BMG with plasticity (collaboration with Shanghai university)
plastic > 0.07
Perspectives / scientific
64
Poisson ratio … deformation mechanism
Yoshida et al., JMR 2005
Lewandowski et al., Phil. Mag. 2005
Pd
65Crystallisation
Three crystallization events may occur at higher temperature…
Analyze here the two first crystallization peaks
250 300 350 400 450 500 550Temperature (°C)
En
do
ther
mic
he
at f
low
(a.
u)
DSC scan at 10°/min. / amorphous sample
Tg ≈ 365 °C
Tp1 = 438 °C
Tp2 = 457 °C
Tp3 = 505 °C
Isothermal Annealing at 410°C
0 20 40 60 80 100
Annealing time (min.)
En
do
ther
mic
hea
t fl
ow
(a.
u.)
_
66DMA / Activation energy
Activation energy:
T<Tg : Q ≈ 100 kJ/mol
**
1' "J J iJ
G " 1J
Ju Maxwell
model 0ln( ) ln( )"
Ju Q
J RT and
Calculation of the activation energy in Small deformation
-5
-3
-1
1
3
5
1,3 1,35 1,4 1,45 1,5 1,55 1,6 1,65 1,7
1000/T (K-1)
ln(J
u/J
")
T = Tg
T > Tg T < Tg
Activation energy:
T > Tg : Q ≈ 450 kJ/mol
DMA / Temperature scan
67
1,E+09
1,E+10
1,E+11
1,E+12
1,E+13
340 350 360 370 380 390 400
temperature (°C)
N (
Pa
.s)
ISMANAM (2006)
Activation energies in SLR measured by two ways
Effect of crystallization : Newtonian Viscosity
Amorphous
Fv = 32 %
Influence of the temperature on the reinforcement
68Effect of the deformation on the crystallization
Materials Science and Engineering A (2006)
No visible influence of the deformation on the crystallization
Reinforcement factor as a function of time.Cristallisation proceed while deforming
69Effect of the deformation on the crystallization
Materials Science and Engineering A (2006)
DRX on two samples DSC on four samples
No visible influence of the deformation on the crystallization
70
Deformed
Effect of the deformation on the crystallization
Materials Science and Engineering A (2006)
No visible influence of the deformation on the crystallization
71High temperature Mechanism
Multiatomic approach of the high temperature deformation
Multiatomic deformation mechanism
High apparent activation energy
Shear model of Argon Resistance of the surrounding
i
i
ii
Qapparent = Q (interfacial shear resistance) + Q (mechanical resistance of the
surrounding)
72High temperature Mechanism
Evolution of the activation energy
Température
En
erg
ie d
'ac
tiva
tio
n
Glassy state Supercooled liquid Liquid state
Tg Tf
Eact:T < Tg
Eact T > Tf
Eact T > Tg
Continuous decrease ?
Mechanical resistance of the surrounding is decreasing
73High temperature Mechanism
Defect concentration evolution
0
0,05
0,1
0,15
0,2
0,25
0,3
-250 -50 150 350 550 750
température (°C)
De
fec
t c
on
cen
tra
tio
n Equilibrium defect concentration
Out of equilibrium concentration
1
1 exp( )exp( )
ed
f f
CH S
RT R
Hf = 14 kJ /mol
Sf = 6 J /mol/°C
74Co-extruded materials
75Co-extruded materials
76Co-extruded materials
77Co-extruded materials
78Co-extruded materials