Crystallization and high-temperature deformation behavior of Cu49Zr45Al6 bulk metallic glass within supercooled liquid region

Abstract

Crystallization and plastic deformation of a Cu49Zr45Al6 ternary bulk metallic glass were investigated within a supercooled liquid region. In isochronal annealing processes, effective activation energies for the primary crystallization of Cu49Zr45Al6 ternary bulk metallic glass were calculated to be over 367kJ/mol, which is quite high compared with other Cu–Zr-based bulk metallic glasses. Based on isothermal transformation kinetics described by the Johnson–Mehl–Avrami model, Avrami exponent (n) was calculated to be between 2.52 and 3.50, indicating that crystallization mechanism showed a diffusion-controlled growth with increasing nucleation rate. The appropriate working temperature-strain rate combination for feasible solid-to-solid forming without in situ crystallization was deduced by constructing a process map superimposed on a time–temperature transformation curve, thereby indicating phase crystallization. Furthermore, the actual solid-to-solid formability around this processing window was confirmed by overlapping the laboratory-scale extrusion ability.