Effect of grain size on strength and strain rate sensitivity in the CrMnFeCoNi high-entropy alloy

It was shown recently that the grain size contribution to the flow stress and strain rate sensitivity of pure metals having different structures can be estimated by a model of deformation for grain boundary sliding. The present research extends this earlier study by estimating the grain size contribution to the flow stress in the CrMnCoFeNi high entropy alloy. This alloy has attracted significant attention in recent years due to its remarkable mechanical properties which include a higher strength compared to f.c.c. pure metals due to a significant contribution from solid solution strengthening. The present work demonstrates that the flow stress of the CrMnCoFeNi alloy can be readily estimated from the sum of the contributions from solid solution and grain size strengthening. There are some unique experimental trends observed in this alloy and these provide supporting evidence for the assumption that the grain size strengthening is thermally-activated. The flow stress, strain rate sensitivity, activation volume and activation energy are predicted for different grain sizes and testing conditions as a function of the fundamental properties of this alloy and the results show excellent agreement with the reported experimental data.