Theoretical model for creep behaviors of CoCrFeMnNi high entropy alloys

Abstract

3-power law creep of high entropy alloys (HEAs) is different from that of conventional alloys. In order to help comprehend the relation between microstructure evolution and macroscopic creep response, three dominant mechanisms related to dislocation movements are considered in this work, i.e. dislocation climb, thermally activated dislocation glide and viscous glide. Thereinto, the influence of dislocation viscous glide on the evolution of dislocation density and velocity is systematically analyzed. For the former, the time effect of viscous glide is taken into account in the derivation of the static recovery term for dislocation density evolution. For the latter, dislocation viscous glide can lead to the reduction for dislocation climb velocity due to the drag effect of solute atmosphere, and the dislocation glide velocity is controlled by the competition between the preparation stage for dislocation climb or thermally activated dislocation glide and viscous glide. To validate the developed creep model, experimental data of CoCrFeMnNi HEAs for both the high stress region ($n\approx 5$) and low stress region ($n\approx 3$) has been considered. A good agreement is achieved between the theoretical results and experimental data, which offers a solid basis to further analyze the effect of dislocation viscous glide from the aspect of microstructure evolution for HEAs.