Enhancing mechanical properties in Co-free medium-entropy alloys through multi-phase structural design

Abstract

Pursuing cost-effective multicomponent alloys with superior properties has sparked interest in exploring Co-free alternatives. In this work, a notable structural evolution from a coarse columnar face-centered cubic (FCC) configuration to a refined dual-phase microstructure was observed in the as-cast Co-free equiatomic CrFeNi-based multicomponent alloys through the Al and Ti additions. The presence of L12 nanoprecipitates in the FCC matrix and multiscale nanoprecipitates in the body-centered cubic (BCC) matrix led to a substantial threefold increase in hardness and a ∼50% reduction in wear rate. The average friction coefficient (COF) was reduced to ∼0.6877. This alloy demonstrates exceptional compressive properties, with a yield strength of 1140 MPa, ultimate strength of 2569 MPa, and plastic strain of 38%. The yield strength is nearly tenfold higher than that of the CrFeNi alloy. These findings highlight the potential of multi-phase structural design as a promising strategy for the development of wear-resistant multicomponent alloys.