Revealing the deformation mechanisms of the heterogeneous structured CrMnFeCoNi high entropy alloy with ameliorated mechanical and corrosion resistance properties

Abstract

Developing high entropy alloy (HEA) with both high strength and ductility is a longstanding challenge as potential structural materials. The strength and ductility trade-off can achieve via tailoring heterogeneous structures. Herein, a gradient structure with grain size variation from surface to center was successfully introduced into the CrMnFeCoNi HEA by ultrasonic nanocrystal surface modification (UNSM) process. More importantly, the deformation mechanisms and strengthening mechanisms of the heterogeneous structured CrMnFeCoNi HEA during tension were also investigated. Experimental results demonstrated that the heterogeneous structured CrMnFeCoNi HEA shows excellent strength and ductility combination properties ascribed to the grain refinement strengthening, dislocation density strengthening, and twinning strengthening. Besides, the corrosion resistance properties are also simultaneously improved, resulting from the low surface roughness, small grain size, and large compressive residual stress value. During tensile deformation process, the deformation mode is the dislocation slip at low strain and the slip system of the alloy is mainly {111}〈110〉. With the increase of deformation amount, twin crossing occurs, and grain size gradually decreases. The deformation mode changes from dislocation slip to twinning at high strain. In conclusion, the UNSM process ameliorates the comprehensive mechanical and corrosion resistance properties of CrMnFeCoNi HEA.