Septenary Zr–Hf–Ti–Al–Co–Ni–Cu high-entropy bulk metallic glasses with centimeter-scale glass-forming ability

Abstract

A new Zr35Hf17.5Ti5.5Al12.5Co7.5Ni12Cu10 high-entropy bulk metallic glass with glass-forming ability up to centimeter scale (diameter of 18 mm) and configuration entropy of 1.77R was discovered. This high-entropy bulk metallic glass differs from previous ones because it was designed to possess a non-equiatomic eutectic composition and was free from Be. The high-entropy alloy exhibited excellent glass-forming ability despite its lower reduced glass transition temperature than those of prototypical glasses. Molecular dynamics simulations suggested that the excellent glass-forming ability was caused by the similar magnitude of the decrease in Hamiltonian from amorphous to crystalline phases to that of a reference ternary bulk metallic glass, as well as the sluggish crystallization of the high-entropy bulk metallic glass.