Texture evolution, deformation mechanism and mechanical properties of the hot rolled Mg-Gd-Y-Zn-Zr alloy containing LPSO phase

Abstract

The texture evolution, crystal orientation-dependent deformation mechanism and mechanical properties of the Mg-5.5Gd-4.4Y-1.1Zn-0.5Zr (wt%) alloy sheet with bimodal grain structure during hot rolling were investigated in this study. The pre-rolled sheet possesses the texture with c-axis randomly distributed in rolling-transverse plane. During the hot rolling deformation, the initial texture is gradually changed to an uncommon texture with c-axis continuously distributed between transverse direction (TD) and normal direction (ND) of the rolled sheet. The formation of the texture is related to the orientation-dependent deformation mechanism of coarse grains. For the coarse grains with c-axis close to rolling direction (RD), {10-12} twinning was identified to be the dominated deformation mechanism. With the activation of twinning, the c-axis of the matrix is reoriented towards ND. For the coarse grains with c-axis near TD, prism <a> slip and kink deformation were figured out as the dominated deformation modes. In early stage of the hot rolling deformation, the c-axis of the grains remains in TD with the activation of prism <a> slip. Afterwards, kink deformation activates and the c-axis of the grains is rotated away from TD towards ND with different degrees. In addition, the mechanical properties of rolled sheets were examined and the results demonstrate that yield strength and tensile strength are gradually improved by rolling deformation. Nevertheless, the improvement of yield strength in RD is much greater than that in TD and a serious yield strength anisotropy is shown in the rolled sheet. The strong yield strength anisotropy derives from the variation of texture strengthening in the RD and TD due to the formation the texture with c-axis continuously distributed between TD and ND.