The influence of a secondary twin on the detwinning deformation of a primary twin in Mg–3Al–1Zn alloy

In the present paper, the influence of a { 10 1 ¯ 2 } – { 10 1 ¯ 2 } secondary twin on detwinning of a { 10 1 ¯ 2 } primary twin is systematically investigated by compression along the normal direction (ND) of pre-strained samples at room temperature. Samples containing both a { 10 1 ¯ 2 } primary twin and a { 10 1 ¯ 2 } – { 10 1 ¯ 2 } secondary twin are prepared by pre-compression along the transverse direction (TD) and subsequent re-compression along the rolling direction (RD) of a hot-rolled AZ31 Mg alloy plate at room temperature. Our results show that the introduction of a { 10 1 ¯ 2 } – { 10 1 ¯ 2 } secondary twin into the primary twin can enhance the compression yield strength along the ND. During compression along the ND, the { 10 1 ¯ 2 } – { 10 1 ¯ 2 } secondary twin mainly deforms by { 10 1 ¯ 2 } twinning, forming a { 10 1 ¯ 2 } – { 10 1 ¯ 2 } – { 10 1 ¯ 2 } ternary twin, while detwinning of the { 10 1 − 2 } primary twin also takes place. When a { 10 1 ¯ 2 } – { 10 1 ¯ 2 } secondary twin happens to totally separate a { 10 1 ¯ 2 } primary twin from the matrix, it can serve as a barrier to impede detwinning of this { 10 1 ¯ 2 } primary twin. The { 10 1 ¯ 2 } twinning in a { 10 1 ¯ 2 } – { 10 1 ¯ 2 } secondary twin can induce a preferred distribution of prismatic planes in twinned regions, which is closely related to the activation of preferential twin variants.