Rotational deformation twins in a HfNbTaTiZr refractory high entropy alloy

Results of the analysis of deformation twins formed in a HfNbTaTiZr refractory high entropy alloy during compression deformation at 20 °C – 600 °C are reported. All studied twins were formed by rotation of the matrix crystal lattice around a 〈110〉 pole and have the common reciprocal twinning plane K ₂ = {001} and reciprocal twinning direction η ₂ = <1 1 ¯ 0>. At the same time, the twinning plane K ₁ and direction η ₁ depend on the degree of rotation of K ₂ and η ₂ around the common 〈110〉 pole. The following rotational twinning modes have been identified in HfNbTaTiZr: { 1 1 ¯ 4 }<2 2 ¯ 1 ¯ > (38.94° rotation), { 1 1 ¯ 5 }<5 5 ¯ 2 ¯ > (31.58°), { 1 1 ¯ 6 }<3 3 ¯ 1 ¯ > (26.54°), { 1 1 ¯ 7 }<7 7 ¯ 2 ¯ > (22.84°), and { 1 1 ¯ 8 }<4 4 ¯ 1 ¯ > (20.04°). A rotational mechanism of twinning, with the rotation axis 〈011〉 or 〈001〉, is proposed as an alternative to the commonly accepted shear mechanism.