Effects of high pressure torsion on microstructures and properties of an Al 0.1 CoCrFeNi high-entr opy alloy

High pressure torsion (HPT) under a pressure of 6GPa through 1 and 2 revolutions have been used to follow the evolution of microstructures and properties in an Al0.1CoCrFeNi high-entropy alloy (HEA). The plastic-deformation mechanisms of the HEA include dislocation slip at low strains and twinning at high strains at room temperature. The planar dislocation slip on the normal face-centered-cubic slip system, {111}〈110〉, and nanoscaled deformation twins with a thickness from several nanometers to 40nm, accompanied with some secondary twins. The hardness of the Al0.1CoCrFeNi HEA increases from 135Hv at hot-isostatic pressed (HIPed) state to about 482Hv after HPT processing. The HEAs have a relatively high initial hardness and high work hardening, compared with traditional alloys. The creep resistance of the HEA processed by HPT was determined by a nanoindentation technique. The strain rate sensitivity, m, increases with the decreasing of grain size, for smaller activation volume and the dominant deformation mechanism changing from the dislocation slip to grain-boundary slide. The present results give the plastic-deformation mechanism and mechanical properties evolution of single-phase HEA processed by HPT at room temperature.