Unrevealing grain boundary mobility in the precipitate hardening high entropy alloys.

Exploring the interactions between precipitates and grain boundaries (GBs) is of great important to tailor the high-temperature stability and mechanical property of precipitate hardened alloys. However, the influence of precipitate on GB stability in high entropy alloys (HEAs) is still uncovered at nanoscale. In this work, we investigate the effects of precipitate size and temperature on grain boundary migration (GBM) using molecular dynamic simulations. The results show that the GB stability is improved with the increase of the precipitate size, especially at low temperatures. Compared with the traditional dilute alloys, the strong atomic lattice distortion exits in HEAs, resulting in the localized high tensile/compressive stresses. Thus, GB bends towards the indeterminate direction due to the lattice distortion, different with the case bending towards precipitate in the dilute alloys. In addition, the lattice distortion makes dislocation nucleate at random GB region in HEA, which is different from that in dilute alloys. High temperature reduces lattice distortion and relieves the localized high stresses, thereby inhibits the nucleation rate of dislocations from GB. These results provide the fundamental messages for designing novel HEAs with excellent thermal stability. • Influence of precipitates on GB stability at nanoscale is still uncovered in high entropy alloys. • Complex atomic stress field around precipitate leads to irregularly non-localized deformation of GB. • GB roughness increases due to stress field induced by precipitate and lattice distortion. • High temperature reduces lattice distortion thus relives localized high stress, thereby inhibit dislocation nucleation. [ABSTRACT FROM AUTHOR]