Influence of group IV element on basic mechanical properties of BCC medium-entropy alloys using machine-learning potentials

Abstract

In order to elucidate the origin of excellent mechanical properties of high-entropy alloys (HEA), it is essential to develop the atomic-level depiction of defect structures, taking into account the influence of composition. Especially in body-centered cubic (BCC) HEA an alteration of constituent elements may lead to a dramatic change in the behavior on the macroscopic level. To study that effect, we employed a machine learning technique and constructed highly accurate robust potentials for two BCC medium-entropy alloys: MoNbTa and ZrNbTa. Even though they have close composition, the mechanical properties of the two alloys differ not only quantitatively, but also qualitatively. We show that the group IV element Zr decreases values of bulk and elastic constants. The influence of short-range order on stacking fault and twin boundary energies is discussed. Also, we show the difference in the screw dislocation core shapes between the two alloys. The cores of 〈111〉 screw dislocations in the ZrNbTa case demonstrate a non-compact shape substantially extended on the (110) plane.