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New glass formation ability criterion derived from melt cooling considerations
基于熔体冷却过程考虑的玻璃形成能力判据
Sheng GUO, Chain‐Tsuan LIUDepartment of Mechanical Engineering, The
Hong Kong Polytechnic University郭晟,刘锦川
香港理工大学机械工程学系
C‐MRS Changsha, Jun 20, 2010
Outline Glass forming ability (GFA) GFA criteria Identify the best GFA criteria New GFA criterion Conclusion remarks
“The oldest archaeological finds from Mesopotamiaand Egypt date back to around 3000 b.c.”
“Such a long standing, well‐documented glassworking ability is contrasted by the difficulties we encounter to understand the nature of glass and the essential features of the glass transition.”
P.M.Ossi, Disordered Materials: An Introduction.
Ancient glass objects, hydria, comb decorated bottle and ribbed bowl (I Century AD)
Glass forming ability
Glass forming ability
(Debeneditti & Stillinger
Nature,2001)
cooling
characterizes the ease of glass forming from liquid state;
can be characterized by the critical cooling rate (Rc);
is related but different to thermal stability of glass forming systems
crystalline
amorphous
5
A major concern for the engineering use of bulk metallic glasses (BMGs) is their limited GFA for many glass forming systems
Understanding of glass formation and prediction of GFA are vitally important for developing BMGs with superior GFA for economic manufacturing of BMGs for industrial use
In recent years significant efforts have been devoted to this important area, and a number of GFA criteriahave been developed
Glass forming ability
Glass forming ability criteria based on characteristic temperatures (Tg, Tx, Tm, Tl, etc)
based on dynamic viscosity (m or D, M) based on thermodynamic analysis (∆H, ∆S) based on fundamental properties of
constituent elements (atomic size, electro‐negativity, electron structure)
……
Glass forming ability criteriaCharacteristic temperatures
(Lu & Liu, Intermetallics, 2004)
Tg: glass transition temperature
Tx: onset crystallization temperature (from heating)
Tl: liquidus temperature
Txc: onset solidification temperature (from cooling)
Glass forming ability criteria
Trg=Tg/Tm or Tg/Tl 1969/2000 ∆Trg=(Tx‐Tg)/(Tl‐Tg) 1972 ∆Tx=Tx‐Tg 1993 =Tx/(Tg+Tl) 2002 =Tx/Tl 2005 =Tx/Tg+Tg/Tl 2005 =Tx/(Tl‐Tg) 2006 m=(2Tx‐Tg)/Tl 2007 =Trg(Tx/Tg)0.143 2007 ′=TxTg/(Tl‐Tx)2 2008 =Tg/Tx‐2Tg/(Tg+Tl) 2009 ……
乱“笋”渐欲迷人眼
Characteristic temperature based GFA
Glass forming ability criteria Reduced glass transition temperature
Trg=Tg/Tm(Turnbull, Contemp Phys, 1969)
“If, as we are supposing, I and u both scale, at given ∆Tr, as 1/, then the glass‐forming tendency should increase with the reduced glass temperature, Tg/Tm=Trg”
( )
Glass forming ability criteria Supercooled liquid region
∆Tx=Tx‐Tg(Inoue, J Non‐Crys Solids, 1993 )
Gamma parameterx
g l
TT T
2( ) / 2
x
l l g
x
g
TT TTT
T
Glass forming ability criteria(Lu&Liu, Acta Mater, 2002;Lu&Liu, PRL, 2003)
Liquid phase stability Resistance to crystallization
Glass forming ability criteria Gamma parameter
x
g l
TT T
49 metallic glasses
23 oxide glasses & 25 cryoprotectiveaqueous solutions
Sorted by: Times Cited
Gamma parameter
Glass forming ability criteria Gamma m parameter
2 x gm
l
T TT
(Du, Huang, Liu &Lu, J Appl Phys, 2007)
2x g xm
l l
x g
l
T T TT TT
TT
Identify the best GFA criteria
(Long, et al., Mat Sci Eng A, 2009)
10log cg B RA g: GFA parameters; Rc: critical cooling rate
Comparing R2
Identify the best GFA criteria10log cg B RA
GFA ↗ , Rc ↘, g ↗. For a given alloy, its Rc is fixed. However, different definition of GFA parameter gives different g values. Can they be compared?
(Guo, Lu&Liu, Intermetallics, 2010)
Identify the best GFA criteriaExtreme conditions scenarioTl=Tg: The liquid transforms to glassy state immediately upon cooling from the molten state.
Best GFAmaximal g (g=1)Tx=0: The crystallization is doomed to happen above the absolute zero temperature, and no stable glass can exist.
Worst GFAminimal g (g=0)
Trg, 2, m and are suitable GFA criteria
Identify the best GFA criteria
-4 -2 0 2 4 6 8 10 120.2
0.4
0.6
0.8
1.0
Trg (R2=0.626)
(R2=0.833) 2 (R2=0.874) m (R2=0.892)
g(T g,T
x,Tl)
log10Rc
Trg=Tg/Tl
=Tx/Tl
2=2Tx/(Tg+Tl)m=(2Tx-Tg)/Tl
m has the best correlation to Rc, statistically
Identify the best GFA criteriaCaution with the statistics: the fitting might be biased because most data points are in the good glass formers side, i.e., in the small Rc and high g side.
-4 -2 0 2 4 6 8 10 120.2
0.4
0.6
0.8
1.0
Trg (R2=0.626)
(R2=0.833) 2 (R2=0.874) m (R2=0.892)
g(T g,T
x,Tl)
log10Rc
Trg=Tg/Tl
=Tx/Tl
2=2Tx/(Tg+Tl)m=(2Tx-Tg)/Tl
Does the mathematically fitted log10Rcvs. g relationship physically make sense?
Is there a unique relationship between the GFA parameter and Rc?
Identify the best GFA criteriaNormalized GFA criteria
Best glass formerSiO2
gʹ=1Rc=Rc‐min≈10‐5 K/s
Worst glass formerNi gʹ=0Rc=Rc‐max≈1010 K/s
After the normalization treatment, a unique relationship between the GFA parameter and Rc is obtained
Boundarycondition
Identify the best GFA criteriaNormalized GFA criteria
-4 -2 0 2 4 6 8 10 12
0.0
0.2
0.4
0.6
0.8
1.0
Trg=Tg/Tl
=Tx/Tg
2=2Tx/(Tg+Tl) m=(2Tx-Tg)/Tl
boundary condition
g' (Tg,T
x,Tl)
log10Rc
g'(T
g,Tx,T
l)
log10Rc
Trg2
m
boundarycondition
Among the mathematically fitted g’ vs. Rc relationship, m has the smallest deviation to the boundary condition, recalling that m also has
the best statistical correlation to Rc.
m is identified as the best characteristic temperatures based GFA criterion
Not end of story though!!(Guo, Lu&Liu, Intermetallics, 2010)
Scattered data points
Best‐fit lines to the scattered data points
New GFA criterionProblems with m
2x g xm
l l
x g
l
T T TT TT
TT
Why Tx has a role in the GFA expression?
Tx actually characterizes the stability against crystallization in the reheating of amorphous solids, while GFA is essentially defined from the molten liquid cooling process.
However, Tx containing GFA parameters are generally superior than those non‐Tx containing parameters (GFA is defined by the competition of forming glassy phase and crystalline phase).
Why Tx appears twice in the m expression?
Can m be further improved based on understanding of the above two issues?
New GFA criterion
-6 -4 -2 0 2 4 6 8 10 12-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2-0.2
0.0
0.2
0.4
0.6
0.8
1.0
Tx/Tl (R2=0.84)
(Tx-Tg)/Tl (R2=0.70)
Boundary condition
g'(T
g,Tx,T
l)
log10Rc
(b)
Tx/Tl (R2=0.84)
(Tx-Tg)/Tl (R2=0.70)
g(T g,T
x,Tl)
(a)
Revisit m2x g x
ml l
x g
l
T T TT TT
TT
Both (Tx‐Tg)/Tl and Tx/Tl are related to RcTx/Tl has a better correlation to Rc than (Tx‐Tg)/TlTx/Tl overestimates the Rcwhile (Tx‐Tg)/Tlunderestimates it.Naturally, a compromise between them would generate a parameter correlating to Rc better.
New GFA criterionConsideration from cooling: Is (1+)Tx corresponding to a characteristic temperature characterizing the cooling process?
Txc=(1.5‐1.7)TxTx: onset crystallization temperature from heating
Txc: onset crystallization temperature from cooling
xc gs
l
T TT
(Guo&Liu, Intermetallics, 2010, in press)
New GFA criterionPhysical meaning of s
( ) ( )xc gs
l
g l xc
l
lT T T TT TT T
Supercooled LiquidGlass Liquid
0 Tg Tl Ti
form glass
Crystal UndercooledLiquid Liquid
0 Txc Tl Ti
form crystal
Glass formation
Crystallization
Supercooled LiquidGlass Liquid
0 Tg Tl Ti
form glass
Crystal UndercooledLiquid Liquid
0 Txc Tl Ti
form crystal
Glass formation
Crystallization
The competition between the undercooling to form glass or to form crystal determines the GFA.
New GFA criterion
Compared to m, (1.5Tx‐Tg)/Tl has the similar correlation coefficient to Rc, while it has much agreement with the boundary condition.
New GFA criterion:5 3 2
21. x g x g
cl l
T T T TT T
(Guo&Liu, Intermetallics, 2010, in press)
Concluding remarks The merit of GFA criteria shall be determined from both the statistical
consideration and the agreement to the physically accepted boundary condition;
There exists an approximate relationship between Tx and Txc: Txc=(1.5‐1.7)Tx;
Defined from the melt cooling process rather than from the reheating process, a new GFA parameter is suggested: s=(Txc‐Tg)/Tl, which in practice can be approximated by c=(3Tx‐2Tg)/Tl.
Things remain unclear: Physics behind s needs to be further understood. What can s tell us on predicting GFA? GFA parameter are unitless while Rc has the unit of K/s?
Thanks for your attention !Sheng GUO(郭晟)
E‐mail: [email protected] thinking people want to get at the essence. They seek it like hidden treasure, which lies at the heart of things and controls them.
‐A Spirkin
, and not falling asleep