Effect of multiple oxides on the mechanical properties of CoCrFeMnNi high-entropy alloy matrix composites

Abstract

This study investigates the oxide formation behaviour and mechanical properties of oxidedispersion-strengthened (ODS) CoCrFeMnNi high-entropy alloy (HEA) matrix composites produced via powder metallurgy. Grain boundary strengthening, solid solution hardening, and precipitation hardening were controlled by varying the duration of mechanical milling and heat treatment durations. The grain size decreased significantly upon milling and it increased to the range of hundreds of nanometres with the heat treatment. Although ex situ-added Y 2 O 3 nanoparticles were uniformly dispersed in the HEA matrix regardless of the milling duration and heat treatment time, different types of in situ oxides, such as Cr-and Mn-oxides, were formed during the heat treatment. Longer milling times led to more crystal defects (e.g. grain boundaries and dislocations) and stored energy in the HEA matrix, thereby stimulating second phase precipitation and oxide formation. Under optimal conditions, the ODS-HEA composites exhibited a good balance between yield strength and elongation in compression.