Experimental and molecular dynamics simulation study on the glass formation of Cu-Zr-Al alloys

LCR Aliaga and LVPC Lima and GMB Domingues and IN Bastos and GA Evangelakis, MATERIALS RESEARCH EXPRESS, 6, 045202 (2019).

DOI: 10.1088/2053-1591/aaf97e

Alloys based on Cu-Zr-Al are known for their relative easiness in producing glassy structures. However, several important aspects related to the microstructure and the Glass Forming Ability (GFA) are still not well understood. Here, we present results referring to Molecular Dynamics simulations (MD) of rapidly quenched glassy Cu-Zr-Al of two compositions. GFAs were investigated, both experimentally and by MD simulations, using x-ray diffraction, High-Resolution Transmission Electron microscopy and Differential Scanning Calorimetry, while the structural evolution upon cooling was investigated by simulations using radial distribution functions, Voronoi tessellation analysis, and volume-temperature curves. Moreover, the viscosity evolution as well as the glass transition temperature and the fragility parameters were also estimated. Good agreement was found between the MD simulation results and the experimental data. It came out that the Zr-rich composition resulted in a 'stronger' metallic liquid than the Cu-rich composition. In addition, we found that the evolution of distorted into well shaped icosahedral clusters upon solidification, is a determining factor for the stability of the Zr-rich metallic glass. Moreover, we propose a new criterion based on a weighted average of the atomic radius ratio that has been found promising in adequately predicting glass forming abilities.

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