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.

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.

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-forming ability of Pr–(Cu,Ni)–Al alloys in eutectic system

2003 ◽  
Vol 18 (3) ◽  
pp. 664-671 ◽  
Author(s):  
Y. Zhang ◽  
H. Tan ◽  
H. Z. Kong ◽  
B. Yao ◽  
Y. Li
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Eutectic Composition ◽  
Solidus Temperature ◽  
Eutectic Point ◽  
Glass Forming Ability ◽  
Al Alloys ◽  
Eutectic System ◽  
Glass Forming

A eutectic point in Pr-rich Pr-(Cu,Ni)-Al alloys was experimentally determined by measuring the solidus temperature (Tm) and liquidus temperature (T1). It was found that Pr68(Cu0.5Ni0.5)25Al7 (at.%) is at the eutectic composition in the pseudoternary Pr–(Cu0.5Ni0.5)–Al alloys. The alloy Pr68(Cu0.5Ni0.5)25Al7 exhibits better glass-forming ability (GFA) than the ternary eutectic alloy Pr68Cu25Al7. However, the best GFA was obtained at an off-eutectic composition (Pr54[Cu0.5Ni0.5]30Al16) in the Pr–(Cu0.5Ni0.5)–Al alloys, which can be formed in fully amorphous rods with diameter of 1.5 mm by copper mold casting. Moreover, the glass-transition temperature Tg increases quickly (from 367 to 522 K) with the increasing of the Al content (from 3 to 27 at.%). The deviation of the best GFA composition from the eutectic point [Pr68(Cu0.5Ni0.5)25Al7] was explained in terms of the asymmetric coupled eutectic zone, the competition between growth of crystalline phase and formation of amorphous, and the higher glass-transition temperature Tg on the hypereutectic side.

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.

GLASS FORMING ABILITY OF HARD MAGNETIC Nd55Al20Fe25 BULK GLASSY ALLOY WITH DISTINCT GLASS TRANSITION

2005 ◽  
Vol 19 (22) ◽  
pp. 3493-3500 ◽  
Author(s):  
L. XIA ◽  
C. L. JO ◽  
Y. D. DONG
Keyword(s):  
Glass Transition ◽  
Glassy Alloy ◽  
Bulk Sample ◽  
Glass Forming Ability ◽  
Glassy Matrix ◽  
Section Thickness ◽  
Xrd Pattern ◽  
Glass Forming ◽  
Bulk Glassy Alloy ◽  
Hard Magnetic Properties

Nd 55 Al 20 Fe 25 bulk sample was prepared in the shape of rods 3 mm in diameter by suction casting. The sample exhibits typical amorphous characters in XRD pattern, distinct glass transition in DSC traces and hard magnetic properties. The distinct glass transition, which is invisible in DSC traces of previously reported Nd — Al — Fe ternary BMGs, allows us to investigate the glass forming ability (GFA) of Nd 55 Al 20 Fe 25 alloy using the reduced glass transition temperature Trg and the recently defined parameter γ. However, it is found that the obtained diameter of the Nd 55 Al 20 Fe 25 glassy rod is much larger than the critical section thickness of the BMG predicted by either Trg or γ. The microstructure of Nd 55 Al 20 Fe 25 as-cast rod was studied and the apparent GFA of the alloy was supposed to be enhanced by the metastable nano-precipitates dispersed within the glassy matrix.

On The Glass Forming Ability Criteria Of Bulk Metallic Glasses

2002 ◽  
Vol 754 ◽  
Author(s):  
Z. P. Lu ◽  
C. T. Liu
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Metallic Glasses ◽  
Glass Formation ◽  
Liquidus Temperature ◽  
Bulk Metallic Glasses ◽  
Glass Forming Ability ◽  
Glass Forming ◽  
Onset Crystallization Temperature ◽  
New Criterion

ABSTRACTA new criterion γ, defined as Tx/(Tg+Tl) (where Tx is the onset crystallization temperature, Tg the glass transition temperature and Tl the liquidus temperature), has been proposed for glass formation in bulk metallic glasses (BMGs). The interrelationship between this new parameter and glass-forming ability (GFA) was elaborated and discussed in comparison with other established criteria. It was found that the new criterion γ had a much better correlation with GFA than other established parameters. An approximation of the critical cooling rate for glass formation was also formulated and evaluated in the light of this new parameter.

Effect of Compositional Short Range Order on Glass Formation in Binary Metallic System

2002 ◽  
Vol 754 ◽  
Author(s):  
Hao Chen ◽  
Mahadevan Khantha ◽  
Takeshi Egami
Keyword(s):  
Glass Transition ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Glass Formation ◽  
Short Range ◽  
Short Range Order ◽  
Glass Forming Ability ◽  
Range Order ◽  
Dynamics Simulation ◽  
Glass Forming

ABSTRACTMolecular Dynamics simulation was carried out to study the glass transition and crystallization in the metal-metalloid binary system with pair-wise potentials. The results show that a repulsive potential between metalloid (small) atoms increases the glass forming ability. The observation is consistent with the recent theory of bulk metallic glass formation through local glass transition and nano-glass formation. The theory predicted that the compositional short-range order (CSRO) prevents the small atom pairing so as to increase the glass forming ability (GFA). The present results demonstrate the important role of CSRO in bulk metallic glass formation.

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