Thermodynamics and Glass Forming Ability from the Liquid State

1998 ◽  
Vol 554 ◽  
Author(s):  
P. J. Desre
Keyword(s):  
Preexponential Factor ◽  
Interface Energy ◽  
Glass Forming Ability ◽  
Undercooled Liquid ◽  
Bulk Glass ◽  
Specific Mechanism ◽  
Number Of Components ◽  
Glass Forming ◽  
Crystal Interface ◽  
Versus Concentration

AbstractThis study is mainly devoted to the establisment of relations between easy glass forming ability of some multicomponent liquid alloys and strong heteroatomic bonding in connection with nucleation. The chemical short range order in typical liquid bulk glass formers as Zr-Ni-AI is evaluated from a statistical model and presented as Cowley's order parameters versus concentration. The effect of the nature and of the number of components on the chemical contribution to the liquid-crystal interface energy and on the Gibbs energy of crystallisation is analysed and discussed. A specific mechanism of nucleation based on a distribution of concentration fluctuations in the undercooled liquid is proposed. This homophase fluctuation mechanism, which is thermodynamically and kinetically justified, leads to a lower preexponential factor in the expression of the frequency of nucleation as a function of the number of components. Furthermore, this frequency of nucleation can be strongly lowered by an augmentation of the energy barrier of nucleation depending on the nature and the number of components in the liquid phase.

Effect of Er doping on glass-forming ability of Co50Cr15Mo14C15B6 alloy

2006 ◽  
Vol 21 (4) ◽  
pp. 958-961 ◽  
Author(s):  
H. Men ◽  
S.J. Pang ◽  
T. Zhang
Keyword(s):  
Glass Formation ◽  
Eutectic Composition ◽  
Critical Diameter ◽  
Alloy System ◽  
Glass Forming Ability ◽  
Undercooled Liquid ◽  
Bulk Glass ◽  
Er Doping ◽  
Glass Forming ◽  
Er Doped

Bulk glass formation of the Co–Cr–Mo–C–B–Er alloy system was investigated in this paper. The Co50Cr15Mo14C15B6 (at.%) alloy could be cast into fully glassy rod with a diameter up to 2 mm. By adding 2 at.% Er to this alloy, the critical diameter for glass formation reached 10 mm. The excellent glass formability of the Er-doped alloy was mainly attributed to its relatively large reduced glass transition temperature of 0.61, near-eutectic composition, and the necessity of redistribution of the Er atoms for precipitation of crystalline Co6Mo6C phase in the undercooled liquid on cooling.

Glass Formation and Glass Forming Ability of Alloys Near Eutectic Composition

2000 ◽  
Vol 644 ◽  
Author(s):  
Y. Li
Keyword(s):  
Glass Transition ◽  
Glass Formation ◽  
Eutectic Composition ◽  
Glass Forming Ability ◽  
Critical Section ◽  
Bulk Glass ◽  
Melting Behaviour ◽  
Eutectic Alloys ◽  
Section Thickness ◽  
Glass Forming

AbstractOnset temperature, Tm and offset temperature (liquidus) Tl of melting of a series of bulk glass forming alloys based on La, Mg, and Pd have been measured by studying systematically the melting behaviour of these alloys using DTA or DSC. Bulk metallic glass formation has been found to be most effective at or near their eutectic points and less effective for off-eutectic alloys. Reduced glass transition temperature Trg given by Tg/Tl is found to show a stronger correlation with critical cooling rate or critical section thickness for glass formation than Trg given by Tg/Tm.

scholarly journals Survey of BGFA Criteria for the Cu-Based Bulk Amorphous Alloys

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
D. Janovszky ◽  
K. Tomolya ◽  
M. Sveda ◽  
A. Roosz
Keyword(s):  
Amorphous Alloys ◽  
Critical Thickness ◽  
Glass Forming Ability ◽  
Bulk Glass ◽  
The Real ◽  
Bulk Amorphous Alloys ◽  
Glass Forming ◽  
Versus Plot ◽  
Mismatch Condition

To verify the effect of composition on the bulk glass forming ability (BGFA) of Cu-based alloys, properties have been collected from the literature (~100 papers, more than 200 alloys). Surveying the BGFA criteria published so far, it has been found that the atomic mismatch condition of Egami-Waseda is fulfilled for all the Cu-based BGFAs, the value being above 0,3. The Zhang Bangwei criterion could be applied for the binary Cu-based alloys. The Miracle and Senkov criteria do not necessarily apply for Cu based bulk amorphous alloys. The critical thickness versus plot of Lu and Liu extrapolates to , somewhat higher than the 0.33 value found in other BGFA alloys. The Park and Kim parameter correlates rather poorly with the critical thickness for Cu based alloys. The Cheney and Vecchino parameter is a good indicator to find the best glass former if it is possible to calculate the exact liquids projection. In 2009 Xiu-lin and Pan defined a new parameter which correlates a bit better with the critical thickness. Based on this survey it is still very difficult to find one parameter in order to characterize the real GFA without an unrealized mechanism of crystallization.

Glass Forming Ability of Ca-Based Bulk Metallic Glasses

2011 ◽  
Vol 171 ◽  
pp. 121-126 ◽  
Author(s):  
Ashmi T. Patel ◽  
Kirit N. Lad ◽  
Arun Pratap
Keyword(s):  
Metallic Glasses ◽  
Driving Force ◽  
Bulk Metallic Glasses ◽  
Energy Difference ◽  
Glass Forming Ability ◽  
Point Of View ◽  
Undercooled Liquid ◽  
Free Energy Difference ◽  
Glass Forming ◽  
Gibbs Free Energy Difference

Knowledge of glass forming ability (GFA) of amorphous metallic alloys is very important from both theoretical and practical point of view. Thermodynamically, the Gibbs free energy difference, ΔG between the undercooled liquid and the corresponding crystalline state is driving force for crystallization. As a consequence, it is a good indicator for glass forming ability of metallic glasses. A novel expression for ΔG has been used to estimate the GFA of recently developed Ca-based bulk metallic glasses viz. Ca53Mg23Cu24,Ca65Mg15Cu20,Ca40Mg25Cu35, Ca50Mg22.5Cu27.5 and Ca55Mg15Cu30. Different GFA criteria are also evaluated for systems taken up in the study and effect of addition of variation in composition of Ca-Mg-Cu system is also investigated. Present work suggests that among different GFA criteria, ΔG is the best criterion for the prediction of GFA for Ca-based bulk metallic glasses.

Mg–Ca–Zn Bulk Metallic Glasses with High Strength and Significant Ductility

2005 ◽  
Vol 20 (8) ◽  
pp. 1935-1938 ◽  
Author(s):  
X. Gu ◽  
G.J. Shiflet ◽  
F.Q. Guo ◽  
S.J. Poon
Keyword(s):  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Mass Density ◽  
High Strength ◽  
Light Metal ◽  
Glass Forming Ability ◽  
Bulk Glass ◽  
Bulk Amorphous Alloys ◽  
Specific Strength ◽  
Glass Forming

The development of Mg–Ca–Zn metallic glasses with improved bulk glass forming ability, high strength, and significant ductility is reported. A typical size of at least 3–4 mm amorphous samples can be prepared using conventional casting techniques. By varying the composition, the mass density of these light metal based bulk amorphous alloys ranges from 2.0 to 3.0 g/cm3. The typical measured microhardness is 2.16 GPa, corresponding to a fracture strength of about 700 MPa and specific strength of around 250–300 MPa cm3/g. Unlike other Mg- or Ca-based metallic glasses, the present Mg–Ca–Zn amorphous alloys show significant ductility.

Bulk glass formation in the Ni–Zr–Ti–Nb–Si–Sn alloy system

2004 ◽  
Vol 19 (8) ◽  
pp. 2221-2225 ◽  
Author(s):  
J.Y. Lee ◽  
D.H. Bae ◽  
J.K. Lee ◽  
D.H. Kim
Keyword(s):  
Glass Formation ◽  
Liquidus Temperature ◽  
Eutectic Composition ◽  
Composition Range ◽  
Alloy System ◽  
Glass Forming Ability ◽  
Maximum Diameter ◽  
Bulk Glass ◽  
Glass Forming ◽  
Crystallization Onset

In this study, the effect of addition of Nb on glass formation in Ni–Ti–Zr–Si–Sn alloys has been studied. The composition range for bulk glass formation with Dmax > 2 mm (Dmax, maximum diameter for glass formation by injection cast method) becomes wider when compared with the non-Nb–containing alloy. The ΔTx (= Tx – Tg; Tx, crystallization onset temperature; Tg, glass transition temperature), Trg (= Tg/Tl; Tl, liquidus temperature) and γ [= Tx/(Tl + Tg)] values for the alloys Dmax > 2 mm are in the range of 40–59, 0.638–0.651, and 0.410–0.419, respectively. The compositions of the alloys (Dmax > 2 mm) are closer to pseudo-eutectic composition than that of the alloy without Nb, showing an improved glass forming ability. The critical cooling rate for glass formation (Dmax = 5 mm) is estimated to be order of approximately 40 K/s.

Bulk Glass Formation in an Fe-Based Fe–Y–Zr–M (M = Cr, Co, Al)–Mo–B System

2004 ◽  
Vol 19 (3) ◽  
pp. 921-929 ◽  
Author(s):  
Z.P. Lu ◽  
C.T. Liu ◽  
C.A. Carmichael ◽  
W.D. Porter ◽  
S.C. Deevi
Keyword(s):  
Metallic Glasses ◽  
Glass Formation ◽  
Amorphous Alloys ◽  
High Strength ◽  
Supercooled Liquid ◽  
Glass Forming Ability ◽  
Bulk Glass ◽  
Bulk Amorphous Alloys ◽  
Glass Forming ◽  
Hardness Values

Several new bulk metallic glasses based on Fe–Y–Zr–(Co, Cr, Al)–Mo–B, which have a glass-forming ability superior to the best composition Fe61Zr10Co7Mo5W2B15 reported recently, have been successfully developed. The as-cast bulk amorphous alloys showed a distinctly high thermal stability with glass-transition temperatures above 900 K, supercooled liquid regions above 60 K, and high strength with Vickers hardness values larger than HV 1200. The suppression of the growth of primary phases in the molten liquids and the resultant low liquidus temperatures were found to be responsible for the superior glass-forming ability in these new alloys. It was found that the addition of 2% Y not only facilitated bulk glass formation, but the neutralizing effect of Y with oxygen in the molten liquids also improved the manufacturability of these amorphous alloys.

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