Formation condition and effect on the early stages of plastic deformation of chemical short-range order in Cr-Co-Ni medium-entropy alloy

Abstract

The variation in the chemical short-range order (CSRO) of Cr-Co-Ni medium entropy alloy is investigated by measuring the electrical resistivity at various temperatures. According to the measurements at various cooling rates, the thermodynamic equilibrium at temperatures higher than 1075 K cannot be quenched in most conventional sample preparations. The resistivity quenched at various temperatures increases with decrease in annealing temperature, especially below 873 K. The activation energy of the reaction is determined 240–270 kJ mol−1. The activation energy is almost the same as that of atomic diffusion in the Cr-Mn-Fe-Co-Ni high-entropy alloy, indicating that the electrical resistivity change is associated with the change in the atomic arrangement. Using the results of electrical resistivity measurements, the effect of the degree of CSRO on the early stage of plastic deformation was investigated by compression tests on single crystals with varying degrees of CSRO. The critical resolved shear stress and activation volume of the slip are found to be virtually independent of the degree of CSRO. Repetitive strain-rate jump tests indicates that the degree of CSRO does not significantly affect the dislocation motion process in the early stages of the plastic deformation in Cr-Co-Ni medium entoropy alloy.