The texture dependence of strength in slip and twinning predominant deformations of Mg-3Al-1Zn alloy

Abstract

In the present study, the effect of different (0002) distributions (<0002> // ND (MT texture) and <0002> // ND together with <0002> // RD (BT texture)) on strength of slip and twinning predominant deformations of a Mg AZ31 plate was systematically studied. The results show that the tensile yield strengths along the TD are similar in the two textures, but yield strength in compression along the TD is obviously higher in BT texture than in MT texture. Here, TD, RD and ND refer to the transverse direction, rolling direction and normal direction of the AZ31 plate, respectively. An analysis on Schmid factors demonstrates that the different compression yield strengths in the two texture mainly results from their different boundary obstacle effect against {101̅2} twinning. The mechanism was further analyzed by a compound use of the activation stress difference of slip/twinning (ΔStress) and geometrical compatibility factor (m′) between neighboring grains. A lower ΔStress or a higher m′ mean a lower boundary obstacle effect. There is a similar ΔStress in the two texture under compression, but an obvious lower m′ in BT texture than that in MT texture. The lower m′ in BT texture than in MT texture leads to a higher boundary obstacle effect and the resultant higher compressive yield strength in BT texture. It is found that the presence of a large number of neighboring grains with a high angle between their c-axes in BT texture mainly accounts for the lower m′.