Molecular dynamics simulations on the tension and compression deformation of TiZrHf HCP medium entropy alloy

In this work, the deformation modes in TiZrHf MEA (medium entropy alloy) under tensile loading and compressive loading were investigated by molecular dynamics simulations. The orientation effect on the mechanical response was revealed by changing the orientation angle θ between c-axis and loading direction. Under tensile loading, the deformation mode changes from \(\left\{ {10\overline{1}2} \right\}\) tension twin at θ ≤ 30° into recrystallization at θ = 45° and \(\left\{ {10\overline{1}1} \right\}\) compression twin at θ = 60–75° and BCC phase transformation at θ = 90°. The nucleation stress of these deformation modes is always decreasing as the orientation angle increases. Under compressive loading, the deformation mode changes from \(\left\{ {10\overline{1}1} \right\}\) compression twin at θ ≤ 30° to basal dislocations at θ = 45–60° and \(\left\{ {10\overline{1}1} \right\}\) compression twin at θ = 75° and BCC phase transformation at θ = 90°. The nucleation stress first increases then decreases and finally increases with the increasing orientation angle. From the nucleation stress, strong anisotropy is observed on the mechanical response. However, tension–compression asymmetry is observed only for small orientation angle and large orientation angle.