Short range ordering and strengthening in CoCrNi medium-entropy alloy

Abstract

The CrCoNi medium-entropy alloy is found to exhibit higher incipient plastic strength by slow cooling after the homogenization treatment. Compared with water quenching, this strengthening originates from the inconsistency of the residual stress and short-range orderings (SROs). By deconvolution of the density distribution of the critical shear stress for the first pop-in, two peaks corresponding to homogeneous and heterogeneous dislocation nucleation, respectively, are suggested. Combining the mean, areal fraction, and activation volume of the two peaks, the roles of residual stress and SROs were quantified. Here, for SRO that increases the critical shear stress for heterogeneous and homogeneous nucleation by 22.4% and 39.9%, the residual stress is negligible for the 2.1% strengthening of both. As a result, slow cooling promotes the formation of SRO in CrCoNi, which is of immense benefit to elevate its properties.