The Importance of Transient Nucleation and Non-Equilibrium Viscosity for Glass Formation

1985 ◽  
Vol 57 ◽  
Author(s):  
Kenneth F. Kelton
Keyword(s):  
Steady State ◽  
Metallic Glasses ◽  
Glass Formation ◽  
Volume Fraction ◽  
Molecular Cluster ◽  
Transient Effects ◽  
Glass Forming ◽  
Model Glass ◽  
Transient Nucleation ◽  
Non Equilibrium

AbstractThe process of nucleation and growth in glasses and undercooled liquids is modeled by directly simulating the evolution of the molecular cluster distribution under both isothermal and non-isothermal conditions. Results of that simulation for the nucleation rate during the quench, and for the number of nuclei produced and the volume fraction transformed at the end of the quench are presented. The following three points are discussed: (1) The importance of transient, or non-steady state, nucleation rates on glass formation is assessed by considering three model glass forming systems: lithium disilicate, a relatively good glass former, and two metallic glasses, (Au85Cu15)77Si9Gd14 and Au81Si19. (2) Using experimentally determined values for the steady state nucleation rates and growth velocities for Pd40Ni40P20, it is demonstrated that, in agreement with recent experimental results, this alloy may be cycled at rates on the order of 1 K/sec between the melting and glass transition temperatures without crystallization. Transient effects are shown to be unimportant under these conditions in this system. (3) The effect on glass formation of a non-equilibrium viscosity during the quench due to configurational freezing is evaluated by assuming a phenomenological model for the changing viscosity.

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.

Cluster-Based Bulk Metallic Glass Formation in Co (-Fe)-Si-B-Nb Alloy Systems

2007 ◽  
Vol 561-565 ◽  
pp. 1275-1278 ◽  
Author(s):  
Qing Wang ◽  
Chun Lei Zhu ◽  
Yan Hui Li ◽  
Jiang Wu ◽  
Chuang Dong ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Metallic Glasses ◽  
Glass Formation ◽  
Bulk Metallic Glasses ◽  
Ternary Alloys ◽  
Glass Forming ◽  
Binary Clusters ◽  
Composition Formula ◽  
Alloy Systems

The present paper investigates the bulk metallic glass formation in Co-based alloy systems with the guidance of the cluster line and minor-alloying principles. The selected basic ternary Co-B-Si alloy compositions are intersecting points of cluster lines, defined by linking special binary clusters to the third element. Then these basic ternary alloys are further minor-alloyed with Nb and quaternary bulk metallic glasses are obtained only by 4-5 at. % Nb minor-alloying of the basic composition Co68.6B25.7Si5.7 that is developed from dense-packed cluster Co8B3. The bulk metallic glasses are expressed approximately with a unified simple composition formula: (Co8B3)1(Si,Nb)1. In addition, a quantity of Fe substitution for Co further improves the glass-forming abilities.

Transient Nucleation in Devitrification

1993 ◽  
Vol 321 ◽  
Author(s):  
A. L. Greer
Keyword(s):  
Classical Theory ◽  
Heterogeneous Nucleation ◽  
Glass Formation ◽  
Homogeneous Nucleation ◽  
Amorphous Solids ◽  
Crystal Nucleation ◽  
Transient Effects ◽  
Interphase Interface ◽  
Transient Nucleation ◽  
Important Test

ABSTRACTA review is given of transient crystal nucleation in glassy or amorphous solids. The types of behaviour are surveyed. It is shown that the kinetics can be quantitatively modelled and that the matching of experiment and theory provides an important test of the classical theory. Examples are considered of homogeneous nucleation (affecting glass formation), heterogeneous nucleation, and nucleation at an interphase interface. While the emphasis is on transient effects of the kind implicit in the classical theory, it is shown that transients can arise for other reasons as well, thus potentially complicating the interpretation of experiments.

Understanding the Glass-forming Ability of Cu50Zr50 Alloys in Terms of a Metastable Eutectic

2005 ◽  
Vol 20 (9) ◽  
pp. 2307-2313 ◽  
Author(s):  
W.H. Wang ◽  
J.J. Lewandowski ◽  
A.L. Greer
Keyword(s):  
Metallic Glasses ◽  
Glass Formation ◽  
Composition Range ◽  
Intermetallic Phase ◽  
Glass Forming Ability ◽  
Copper Mold ◽  
Wide Composition Range ◽  
Glass Forming ◽  
Copper Mold Casting ◽  
Mold Casting

Interest in finding binary alloys that can form bulk metallic glasses has stimulated recent work on the Cu–Zr system, which is known to show glass formation over a wide composition range. This work focuses on copper mold casting of Cu50Zr50 (at.%), and it is shown that fully amorphous rods up to 2-mm diameter can be obtained. The primary intermetallic phase competing with glass formation on cooling is identified, and the glass-forming ability is interpreted in terms of a metastable eutectic involving this phase. Minor additions of aluminum increase the glass-forming ability: with addition of 4 at.% Al to Cu50Zr50, rods of at least 5-mm diameter can be cast fully amorphous. The improvement of glass-forming ability is related to suppression of the primary intermetallic phase.

Glass formation, thermal properties, and elastic constants of La–Al–Co alloys

2010 ◽  
Vol 25 (7) ◽  
pp. 1398-1404 ◽  
Author(s):  
Ran Li ◽  
Mihai Stoica ◽  
Gang Wang ◽  
Jin Man Park ◽  
Yan Li ◽  
...  
Keyword(s):  
Elastic Constants ◽  
Metallic Glasses ◽  
Glass Formation ◽  
Elastic Moduli ◽  
Bulk Glass ◽  
Compositional Dependence ◽  
Glass Forming ◽  
Characteristic Temperatures ◽  
The Relationship ◽  
Co Alloys

The compositional dependence of glass formation and thermal and elastic properties was clarified for the ternary La–Al–Co bulk glass-forming system. The existing linear correlation between La concentration and characteristic temperatures, i.e., the glass transition temperature Tg and the onset temperature of crystallization Tx, as well as the elastic moduli in this system can give a useful guideline for the chemical design of desirable bulk metallic glasses (BMGs) with tunable physical properties in advance. The relationship between Tg and elastic constants for the La–Al–Co BMGs can be quantitatively described using a microscopic model proposed by T. Egami.

Room-Temperature Mechanical Properties and Glass Formation of Zr50Cu20Ni15Al(15-X)Tix (x=3, 5, 7) Bulk Metallic Glass Alloys

2011 ◽  
Vol 66-68 ◽  
pp. 741-746
Author(s):  
Jia Hua Zou ◽  
Zhi Chen Zhang ◽  
Shu Quan Sun
Keyword(s):  
Mechanical Properties ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Metallic Glasses ◽  
Glass Formation ◽  
Room Temperature ◽  
Glass Forming Ability ◽  
Glass Forming ◽  
Ti Content ◽  
Ti Addition

In the present study, the Zr-Cu-Ni-Al based bulk metallic glasses with different Ti addition was successfully prepared by suction casting . It was found that the glass forming ability was improved with increasing of Ti content from 3 at.% to 7 at.%. However, with increasing of Ti content, the room-temperature plasticity decreased from 4.33% to 0.66 %.

scholarly journals A Local Probe into the Atomic Structure of Metallic Glasses Using EELS

1998 ◽  
Vol 554 ◽  
Author(s):  
F. M. Alamgir ◽  
Y. Ito ◽  
H. Jain ◽  
D. B. Williams ◽  
R. B. Schwarz
Keyword(s):  
Energy Loss ◽  
Metallic Glasses ◽  
Atomic Structure ◽  
Electron Energy Loss Spectroscopy ◽  
Glass Formation ◽  
Slight Modification ◽  
Bulk Glass ◽  
Glass Forming ◽  
Electron Energy Loss ◽  
Extract Information

AbstractElectron energy loss spectroscopy (EELS) is used to extract information on the topological arrangement of atoms around Pd in the bulk-glass-forming Pd60Ni20P20. It is found that the environment around Pd in the glass is only a slight modification of the Pd crystalline structure. However, the modification is enough to allow this alloy to form a glass in bulk. In examining the differences between the structure of crystalline Pd and glassy Pd60Ni20P20 it is concluded that incorporation of Ni and P into the structure frustrates the structure enough that glass formation becomes easy.

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.

Enhancing bulk metallic glass formation in Ni–Nb–Sn-based alloys via substitutional alloying with Co and Hf

2008 ◽  
Vol 23 (3) ◽  
pp. 688-699 ◽  
Author(s):  
Li Zhang ◽  
Mu-Jin Zhuo ◽  
Jian Xu
Keyword(s):  
Metallic Glass ◽  
Ternary System ◽  
Metallic Glasses ◽  
Glass Formation ◽  
Composition Range ◽  
Glass Forming Ability ◽  
Partial Substitution ◽  
Wide Composition Range ◽  
Positive Effects ◽  
Glass Forming

Bulk metallic glasses have been formed over a fairly wide composition range (54–62 at.% Ni, 32–36 at.% Nb, and 3–11 at.% Sn) in the Ni–Nb–Sn ternary system. Partial substitution of Co for Ni and Hf for Nb improves the glass-forming ability, eventually leading to 4 mm glassy rods at the Ni56Co3Nb28Hf8Sn5 composition. The positive effects of these alloying elements have been explained based on a systematic monitoring of the amount and morphology of the competing crystalline phases as a function of the Co and Hf contents.

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