Manipulating grain boundary migration to fabricate integral core–shell structure with enhanced strain hardening in Ni-based high-entropy alloy

Abstract

A core–shell microstructure represents an approach to achieve superior mechanical properties in alloys through its distinctive architecture, typically developed in powder metallurgy processing. In the present study, an integral core–shell structure has achieved in a cast Ni–based high entropy alloy through a straightforward thermo–mechanical processing (TMP) approach, including hot rolling and heat treatment. Inspired by the formation of a necklace structure during the hot deformation, we employed hot rolling to induce bulged grain boundaries in coarse grains. Subsequent heat treatment constrained the growth of these bulged regions through B2 precipitate formation, leading to the stabilization of the integral core–shell structure, where the deformed grains form the core, and the bulged grains form the shell. The significant synergistic hardening from the microstructural heterogeneity of the integral core–shell structure improves strain hardening in the TMP-processed sample. The integrated TMP approach, combined with alloy design, enables the evolution of integral core–shell structures in cast high entropy alloys, significantly improving material properties without the complexities of powder metallurgy.