Tension–Compression Asymmetry of BCC NbMoTaW in High Entropy Alloy Nanowires

In recent years, considerable research efforts have been directed toward addressing the room-temperature brittleness of BCC NbMoTaW refractory high entropy alloys (RHEAs). However, there has been limited investigation of the plastic deformation mechanism at room temperature. In this work, we utilized molecular dynamics simulation to investigate the mechanical behavior and atomistic plastic deformation mechanism of BCC NbMoTaW RHEA nanowires under uniaxial compression/tension. It showed that, under tension, the primary deformation mechanism of the nanowires involves the nucleation and growth of twins from the surface, while under compression, the deformation is predominantly attributed to dislocation slip and twinning, with the twins formed by the dissociation of screw dislocations, differing from the twin nucleation and growth under tension. Furthermore, the tension–compression asymmetry of the nanowires was discussed in detail, considering the atomic arrangement and energy barrier. This work contributes to a deeper understanding of the relationship between the deformation mechanism and mechanical response of NbMoTaW RHEAs, which is significant for their rational design and aerospace applications.