Effect of twins on the crystallographic characteristics of the Mg17Al12 phase in the pre-compressed AZ91 alloy

Crystallographic characteristics of the β-Mg17Al12 phase have been investigated in the pre-compressed and aged Mg-9.0 wt%Al-1.0 wt%Zn alloy. Due to pre-compression, morphologies of the β phases became much wider and shorter. The aspect ratio was reduced dramatically. Besides, octahedron shaped β phase with Crawley OR have been observed and portion of the β phase with Crawley OR increased. The twins generated by compression affect the ORs of the β phase. The OR between the β particle and the {1 0 −1 2} twin is: [1 −2 1 0]α//[1 1 −1]β, (0 0 0 2)α near parallel to (1 −2 −1)β. ORs between β particles and the {1 0 −1 1} twin were more complex. Two typical ORs between the β particles and the {1 0 −1 1} twin have been identified as: [1 −2 1 −3]T//[1 1 0]β1, (1 −1 0 1)T//(3 −3 0)β1 and [1 −2 1 −3]T//[1 1 3]β2, (0 −1 1 1)T//(2 1 −1)β2, which have rarely been reported before.