Unrevealing Grain Boundary Mobility in the Precipitate Hardening High Entropy Alloys

Abstract

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 precipitates on GB stability at nanoscale is still uncovered in high entropy alloys. In this work, we investigate the effects of precipitate size and temperature on GB migration 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 high entropy alloys, resulting in the localized high tensile/compression stresses. Thus, GB bends towards the indeterminate direction due to the lattice distortion, different with the case bending towards precipitate in the dilute alloys. The lattice distortion also makes dislocations nucleate at random GB region in HEA, also different from in dilute alloys. High temperature reduces lattice distortion thus relives localized high tensile/compression stresses, thereby inhibit the nucleation rate of dislocations from GB. These results provide the fundamental messages for designing novel high entropy alloys with excellent thermal stability.

Keywords: High entropy alloy, grain boundary migration, precipitate, temperature, lattice distortion