Optimisation of superplastic processing parameters for a TiZrHfBeCuNi high entropy bulk metallic glass in the supercooled liquid region

Abstract

In this study, the deformation behavior of Ti20Zr20Hf20Be20(Cu10Ni10) high entropy bulk metallic glass (HE-BMG) in the supercooled liquid region was investigated via uniaxial compression tests. The thermal workability was also investigated to determine the optimal range of processing parameters. The results revealed that the deformation behavior in the supercooled liquid region exhibited two modes: flow deformation and brittle fracture, both of which were significantly affected by temperature and strain rate. The homogeneous flow deformation behavior changed from Newtonian to non-Newtonian with a decrease in temperature and an increase in strain rate. The activation volume of the HE-BMG ranged from 0.146 to 0.304 nm3 based on the transition theory of the free volume model, indicating that the atomic group can migrate (about 12–25 atoms) during high-temperature deformation. The fracture surface analysis of the HE-BMG revealed that the fracture angle increases with increasing deformation temperature, which was primarily due to an increase in cohesive strength. The optimal processing parameters for forming HE-BMG without crystallization were determined by constructing a deformation map based on the deformation behavior and microstructural analysis results.