Influence of chemistry and temperature on mechanical behavior and deformation mechanisms of refractory high-entropy alloys: an integrated simulation-modeling analysis

The equiatomic refractory high-entropy alloys (RHEAs) exhibit the excellent performance at high temperatures, breaking through the upper limits of operating temperatures in the conventional high-temperature alloys. Here, the influences of chemistry and temperature on the deformation mechanisms of the equiatomic MoNbTaW RHEAs are investigated, using the large-scale atomic simulations. According to the microstructure evolution, a microstructure-based constitutive model is established to study the effects of the multiple strengthening mechanisms. The results show the jagged sharp fluctuations of the flow stress with the strain after the strain hardening. The increasing temperature reduces the strain-hardening rate and the amplitude of fluctuations in the flow stress, due to the reduction of the solute concentration for the annealed structure. The deformation twinning plays a certain role in the deformation mechanism in comparison with dislocation, and the local deformation is further accommodated via the dislocation-based plasticity, and amorphous nucleation in the grains. The existence of the ordered structure affects the stress and strain partition dependent upon the mechanical properties. The solid solution strengthening and grain boundary strengthening contribute considerably to the flow stress, and twinning strengthening contributes relatively little to the flow stress. Our atomic simulation and model give valuable insights into the deep understanding of chemistry and temperature related to the deformation behaviour of RHEAs.