Effect of grain size on the strain rate sensitivity of CoCrFeNi high-entropy alloy

Abstract

Strain rate sensitivity (SRS) of a face-centered cubic (fcc) CoCrFeNi high-entropy alloy (HEA) with grain sizes ranging from 57 mu m to 45 nm was investigated using nanoindentation, and was compared with those reported for conventional fcc metals. Experimental results show pronounced grain boundary strengthening in the HEA. Estimated values of the SRS parameter, m and activation volume, V*, indicate similar plastic deformation mechanisms in HEA and Ni in nanocrystalline regime that are grain boundary mediated. In coarse-grained regime, the high lattice friction stress in the HEA results in much higher m and smaller V* as compared to coarse grained Ni.