Friction stress and Hall-Petch relationship in CoCrNi equi-atomic medium entropy alloy processed by severe plastic deformation and subsequent annealing

摘要

The present work focuses on the friction stress and the Hall-Petch relationship in CoCrNi equi-atomic medium entropy alloy (MEA). The CoCrNi equi-atomic MEA and a Ni-40Co alloy were processed by high-pressure torsion and subsequent annealing. The specimens with fully-recrystallized microstructure with different grain sizes ranging from 199 nm to 111 mu m were obtained. The Hall-Petch plot of the yield strength of the present specimens indicated that the friction stress of the CoCrNi MEA was much higher than Ni-40Co and pure metals, suggesting that the local lattice distortion in the equi-atomic alloy played an important role for the dislocation activity. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.