Effects of heat treatment parameters and grain sizes on mechanical response of amorphous/crystalline CuZr composites

Abstract

The amorphous phase proportion in nanocrystalline/amorphous CuZr samples was tailored using heat treatment processes under a fast-dynamic regime by varying temperature and time. It was revealed that using molecular dynamics simulations of tension tests, the samples with a larger fraction of crystalline phase exhibit superior mechanical properties. During tension, a dual-slope phenomenon was observed, driven by grain boundary behaviors and subsequent phase transition in the crystalline phase. The plastic deformation was mainly dominated by slip bands generated from dislocation nucleation in the crystalline phase, rather than embryonic shear bands in the amorphous phase. In contrast, the samples with a higher fraction of amorphous phase exhibit softening, leading to reduced mechanical properties. Plastic deformation in these samples is initiated by shear band nucleation in the amorphous phase, which expands within the amorphous phase and induces the formation of slip bands in the crystalline phase, though deformation remains predominantly governed by shear bands. These results can provide insight into the deformation behavior of nanoscale amorphous/crystalline dual-phase CuZr composites and guidance for the structural optimization of high-strength and high-plasticity amorphous/crystalline composites.