Study On Twinning Behavior In Plane Strain Compression Of AZ31 Magnesium Alloys

This paper mainly research on twin behavior and microstructure evolution of magnesium alloys in the plane strain compression(PSC). Here, commercial AZ31 magnesium alloy was used as the initial materials, and small deformation was applied on samples of different orientation in PSC experiment. Optical microscope, electron back scattering diffraction technology and crystallography analysis were used to study orientation microstructure evolution and selection of twin variation regularity in PSC. Through compared with uniaxial compression deformation, twin behavior on macro stress sensitivity is discussed. Paper get the following main conclusions:When TD is compressed and ND is constrained in PSC, extension twin is still the main deformation mechanism. Compared with uniaxial compression along the TD, yield phenomenon of the twin leading is not obvious, but the strain hardening rate is higher. The grains usually contain one or two twin when strain is 3%, and the choice of twins usually follow the Schmid law. The area fraction of twinning was obviously less than that in uniaxial deformation, and these results show that stress along ND improves the nucleation and growth stress of twinning. When TD is compressed and RD is constrained in PSC, prismatic slip is restricted. Compared with uniaxial compression, yield phenomenon is more obvious and the strain hardening rate is low. When strain is 3%, some grains activated three or four variant, which lead the frequency of non-SF twin is higher. The area fraction of twinning is higher than that in uniaxial compression. These results suggest that twin enhance the dominant deformation when RD is constrained in PSC. Compared with uniaxial compression, non-SF twins were more obviously when ND and RD is constrained in two PSC experiment. This suggests that the choice of twin variants were more significantly influenced by the macroscopic stress in PSC, and it is more susceptible to the effect of local strain coordination in uniaxial compression. When TD is compressed and ND is constrained in PSC, twin almost did not happen because of bad orientation. Favorable deformation mechanism is compression twin and cone slip, but they need high shear stress to start. Few contraction twinning is found. It is not easy for contraction twin to broaden, so the texture is not obvious changed.