Enhanced Mechanical Properties of a CoCrNi Alloy with a Gradient Dislocation Structure

Abstract

Herein, a gradient dislocation structure (GDS) with a thickness of about 600 μm is fabricated on the surface of a CoCrNi medium entropy alloy (MEA) using surface mechanical rolling treatment. With increasing depth, the dislocation density of the GDS sample decreases, while the grain size shows no significant refinement except for the topmost layer. The strength of the GDS sample exhibits a pronounced increase while maintaining decent elongation (about 40%) and work-hardening ability, which can be attributed to the numerous dislocation tangles and networks stabilized by the nanoscale chemical short-range ordered structure dispersed in the CoCrNi MEA. The stable dislocation tangles and networks are effective in resisting dislocation motion, thereby contributing to continuous hardening upon strain. These findings provide a promising approach to achieving exceptional strength-ductility synergy in MEA and expanding their potential applications in engineering.