Achieving Unusual Stable Textures in AZ91 Alloy by Asymmetric Hot Rolling

〈0001〉||RD-oriented AZ91 magnesium alloy was produced by asymmetric hot rolling (AHR). The corresponding microstructures and texture evolutions were investigated. It was found twinning acts as an important role at the beginning of the plastic deformation. There were no obvious recrystallization mechanisms in 8% deformed AZ91; on the contrary, partial recrystallization (PSN mode) occurred during 15% hot rolling. Since 〈0001〉 of many grains were parallel to the RD, the Schmid factor of basal slip was about 0, and it was hard to activate basal slip during 8% rolling. It was of special interest to observe that the intensity of basal orientation significantly enhanced from 2.6 × R to 47.7 × R (the letter R means multiple of random distribution) with an increase in the rolling deformation from 8% to 15%. Both extension twinning and {0001} basal slip reoriented the {0001} planes perpendicular to the axis of compression during 15% rolling. In the 15% deformed sample, the increased activity of pyramidal slip led to a splitting of the {0001} pole in the rolling direction. Interestingly, the AZ91 sheets produced by AHR exhibited some unusual stable textures such as \(\{ 30\overline{3}1\}\) $\{30\overline{3}1\}$ ||ND, \(\{ 11\overline{2}4\}\) $\{11\overline{2}4\}$ ||ND, \(\{ 01\overline{1}0\} \langle \overline{2}110\rangle\) $\{01\overline{1}0\}⟨\overline{2}110⟩$ , and \(\{ 01\overline{1}0\} \langle \overline{2}11\overline{6}\rangle\) $\{01\overline{1}0\}⟨\overline{2}11\overline{6}⟩$ . The fiber textures indicated that the {0001}||ND and \(\{ 11\overline{2}4\}\) $\{11\overline{2}4\}$ ||ND fibers were the end and intermediate orientations in the hot-rolled AZ91 alloy.