Superior cryogenic tensile properties of ultrafine-grained CoCrNi medium-entropy alloy produced by high-pressure torsion and annealing

Ultrafine-grained materials with nanotwins are expected to produce a remarkable combination of strength and ductility. In the present study, ultrafine-grained CoCrNi medium-entropy alloy with nanotwins is fabricated by high-pressure torsion followed by annealing; and investigated for cryogenic tensile properties. The alloy exhibits superior cryogenic tensile properties with a tensile strength of similar to 2 GPa and tensile strain of similar to 27%. The cryogenic tensile strength of ultrafine-grained sample increased by 67% as compared to the cryogenic tensile strength of coarse-grained sample due to fine grain size, annealing nanotwins, residual dislocation density, and strong temperature dependence of yield strength. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.