Glass Formation and Structural Study of Ti50Cu50 Alloy by Molecular Dynamics


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Ti-based metallic glasses (MGs) due to their relative low densities exhibit ultrahigh specific characteristics. In this article the glass-forming behavior and atomic structure of Ti50Cu50 MG were investigated through molecular dynamics simulation (MDS) using the general embedded-atom method (GEAM) potential. As observed experimentally, simulated Ti50Cu50 alloy undergoes three states on quenching: (i) equilibrium liquid; (ii) supercooled liquid and (iii) glassy solid. The atomic configuration of the glass was analysed based on the radial distribution function (RDF) and Voronoi tessellation (VT). It was found that there exist a variety of polyhedral units in Ti50Cu50 MG, where distorted icosohedral and bcc clusters are dominant.



Materials Science Forum (Volumes 638-642)

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Edited by:

T. Chandra, N. Wanderka, W. Reimers , M. Ionescu




J. J. Pang et al., "Glass Formation and Structural Study of Ti50Cu50 Alloy by Molecular Dynamics", Materials Science Forum, Vols. 638-642, pp. 1665-1670, 2010

Online since:

January 2010




[15] For example, in Fig. 4(c), the four atoms between the central and topmost atoms do not stay in a plane. Also, the four numbered atoms form an irregular four-edged shape. These irregular geometrical characteristics indicate the existence of non-efficient atomic packing in our amorphous model. Such non-efficient packing can generate more free volume for atomic movement and thus decrease the viscosity of the material during cooling. Thus, from an atomic perspective Ti50Cu50 is not able to form a glass readily. Z=10 Cu Ti (a) Z=11 <0 2 8 1> (b) Z=12 <0 2 8 2> (c) 1 4 3 2 Z=13 <0 1 10 2> (d) Z=14 (e) Fig. 4 Representative polyhedral configurations (a)-(d) extracted from the amorphous model of Ti50Cu50 in this study. (e) The coordination polyhedron in crystalline Ti50Cu50 shown for comparison. From (a) to (d), the coordination numbers are respectively 10, 11, 12, and 13. The connection of atoms by hollow bars indicates close contact of atoms. Further examination of polyhedral configurations, called VT was performed (not shown here), which characterizes the way of how neighboring atoms connect to each other. It was found that distorted icosahedral and bcc clusters are dominant although a large number of polyhedral types exist. In Fig. 4(b)-(d), following the CN is the Voronoi index , where ni stands for the number of i-edged faces of a Voronoi cell and ∑∑∑∑ in is the total CN. The three cells <0 2 8 1>, <0 2 8 2> and <0 1 10 2> are often referred to as icosahedral type. Interestingly, these cells look similar to the crystalline unit (see Fig. 4(e) in geometrical feature and are relatively easy to transform to it by atomic rearrangement. The crystallization mechanism will be the subject of future research. Summary The present study was performed by molecular dynamics simulation and contributes to the knowledge of glass-forming behavior and atomic structure of Ti50Cu50. The understanding of atomic structure is the key to design of a good glass former with desired properties. Some conclusions through this research have been reached: (i) Ti50Cu50 in this simulation shows continuous change in physical properties on rapid cooling and the thermal properties obtained are in good agreement with experimental data. (ii) A MG is a mixed material of liquid and crystal from a structural viewpoint. Ti50Cu50 is not a good glass former according to the reduced glass transition temperature and atomic structure analysis. (iii) There exist a large number of polyhedral configurations in this amorphous model, where distorted icosahedral and bcc clusters dominates. References.

DOI: 10.1103/physrevb.67.144107

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