Compositional effects on the antiphase boundary energies in B2-type NiTi and NiTi-based high-entropy intermetallics

Abstract

High-entropy intermetallics (HEIs) have experimentally exhibited excellent room- and high-temperature strengths. Superior strengths of HEIs are mainly ascribed to the enhanced resistance of dislocation nucleation and slip caused by large antiphase boundary (APB) energies. In this work, first-principles calculations were performed to investigate the compositional effects on the APB energies in B2-type NiTi and NiTi-based HEIs. The site preferences of solutes in NiTi alloy are determined, and the effects of solutes on the APB energies (APBE) are predicted to correlate with their site preference. Solutes with definite site preference enhance the APB energies of NiTi alloy, while solutes possessing composition-dependent site preference reduce the APB energies. Furthermore, the correlations between APB energies, formation enthalpy, and valence electron concentration (VEC) in B2-type intermetallics are established. APB energies decrease with the increasing formation enthalpy in B2-type intermetallics. The VEC-APBE rule shows that B2-type intermetallics with a VEC range of 6–7 possess large APB energies. Our findings provide theoretical basis for composition design of HEIs to achieve superior strength-plasticity synergy.