Icosahedral cluster energetics in Zr₆₀Cu₁₀Al₁₅Ni₁₅ bulk metallic glass and their role on solidification behavior

Abstract

The energetics behind transformation of liquid structure into subsequent intermediate phases during solidification is expected to play a decisive role in glass/crystal formation. A great deal of experimental and simulation work on supercooled liquids has indicated that, there exists a close link between the liquid structure and icosahedral clusters, especially for bulk metallic glass forming liquids. Pertinently, icosahedral clusters are also found to be energetically favorable to form upon devitrification of Zr₆₀Cu₁₀Al₁₅Ni₁₅ glassy alloy. Such evolution of icosahedral clusters upon devitrification in this alloy invariably proves their manifestation at the intermediate stage during transition of supercooled liquid into glass. Hence understanding the energetics behind restructuring of these clusters into glass or crystal during solidification, aids in microstructure optimization of glass/crystal composites for structural and functional applications. In this paper, it has been attempted to investigate the energetics behind the evolution of Zr–Ni and Zr–Al binary intermetallic phases during crystallization of Zr₆₀Cu₁₀Al₁₅Ni₁₅ glassy alloy. Ascalaph Designer Molecular Modeling Suite is used to generate different models of clusters to understand the formation of Zr–Ni and Zr–Al phases. We propose solidification mechanism in this alloy via two steps, namely, formation of intermediate Zr–Cu icosahedral clusters which is structurally restricted process and precipitation of crystalline phases as thermodynamically favorable process.