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 degrees C - 600 degrees 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 K2 = {001} and reciprocal twinning direction eta 2 = <110>. At the same time, the twinning plane K1 and direction eta 1 depend on the degree of rotation of K2 and eta 2 around the common (110) pole. The following rotational twinning modes have been identified in HfNbTaTiZr: {114}<221> (38.94 degrees rotation), {115}<552> (31.58 degrees), {116}<331> (26.54 degrees), {117}<772> (22.84 degrees), and {118}<441> (20.04 degrees). A rotational mechanism of twinning, with the rotation axis (011) or (001), is proposed as an alternative to the commonly accepted shear mechanism.