On the glass-forming ability of (Zr0.5Cu0.5)100- xAlx ternary alloys: A molecular dynamics study

In this research, the atomic scale local structures in (Zr0.5Cu0.5)(100-x)Alx (x = 0,2,4,6,8,10,12) bulk metallic glass was studied using molecular dynamics simulation method. The pair distribution function, Voronoi analysis and mean squared displacement (MSD) were adopted for investigation of the local structures. It was found that Cu and Al-centered full icosahedra possess the most frequency accompanied by the most changes during the glass transition process in the supercooled liquid region temperature. Moreover, it was observed that the Al-centered full icosahedra (Al-FI) and Cu-centered full icosahedra (Cu-FI) clusters with 2.5% and 1.9% increase (relative to total atoms), respectively, have the most increase and are the most geometrically stable structures compared to the other local structures. Therefore, these two structures possess the most effect on the Glass-Forming Ability (GFA) enhancement. The MSD analysis results revealed that the Cu-FI structure compared to the Al-FI and other local structures have higher stability and lower mobility, and its trend as a function of chemical composition can interpret the achieving optimal GFA in the 8% Al composition. Eventually, the cause of reduced mobility and increased stability of the central atoms of Al-FI and Cu-FI structures were evaluated using the distribution of chemical composition. The main reasons that led to the reduced mobility and increased stability of the Al-FI and Cu-FI structures and attainment of the maximum GFA in Zr46Cu46Al8 alloy are: (1) the system possesses the Al-FI structures far apart from each other and has negligible Al atoms in their shell. (2) Then, the new Al atoms insert into the shell of Cu-FI structures in the 8% Al composition. (3) And consequently, the Cu-Al and Zr-Al bond pairs enhance in the shell of Cu-FI clusters.

Automated summary

This research used molecular dynamics simulation method to study the atomic scale local structures in (Zr0.5Cu0.5)(100-x)Alx (x = 0,2,4,6,8,10,12) bulk metallic glass. The study found that Cu-centered and Al-centered icosahedra were the most frequent and experienced the most changes during the glass transition process, and they had the greatest effect on the Glass-Forming Ability (GFA) enhancement. The stability and mobility of the Cu-FI structure were higher compared to the Al-FI and other local structures, and its trend as a function of chemical composition explained the optimal GFA achieved in the 8% Al composition.