چكيده به لاتين
Bulk metallic glasses (BMGs) have attracted significant interest from numerous researchers in recent years because of their exceptional qualities, which include good wear properties, excellent corrosion resistance, high strength and hardness, elastic deformation, and favorable biocompatibility. Nevertheless, there are still two significant obstacles to enhancing the application of these alloys, and they are as follows: 1. when the external stress approaches the yield stress, shear bands are activated, which causes bulk metallic glasses to become very brittle and break easily. 2. The low glass-forming ability of many alloy systems limits the size of the products made from these alloys. Therefore, an understanding of the atomic-scale controlling processes in these alloys is required to overcome the two aforementioned restrictions. It is nearly impossible to obtain a picture of the atomic arrangement at the atomic scale in these materials using standard experimental techniques because of the lack of long-range atomic order in these materials, which makes the experimental investigation of their structure at this scale very difficult and limited.
In this work, the structure and its relationship to thermodynamic parameters at the atomic scale were examined using the molecular dynamics simulation. For this purpose, at first, primary structures were created in different chemical compounds of the Zr-Cu-Al ternary system, and molecular dynamics simulations were performed on these structures. Then the obtained results were analyzed based on the Voronoi analysis method and radial distribution function, and as a result, the vitrification mechanism and the topological and chemical local structures were investigated.
It was found that the composition with 6%Al is the line between the predominance of ideal and non-ideal Cu-FI and Al-FI structures, such that before it, the system tends to increase the chemical ordering of the Cu-FI and Al-FI structures, and in this compositional range, the mentioned structures are approaching the ideal ones. By transitioning from 6% Al to 8% Al, the Voronoi cell volume decreases due to the elemental mixing in the shell of full icosahedra, which means an increase in the configurational entropy. Then, the relative potential energy (as indicator of TSRO) and Voronoi cell volume (as indicator of CSRO) were integrated to obtain a criterion for prediction of GFA. Our new criterion is in good agreement with the reported experimental data. Eventually, this new criterion was employed to predict the glass-forming ability (GFA) for a wide range of Zr-Cu-Al ternary alloys. It was found that Zr46Cu46Al8, Zr70Cu20Al10, and Zr40Cu10Al50 alloys are the optimal compounds with the maximum glass-forming ability (GFA) in the Zr-Cu-Al ternary system.
