Effect of Direct Extrusion and Variable Channel Shear Deformation on Microstructure Evolution of AZ31 Magnesium Alloy Thin-Walled Tubes

In this paper, a new severe plastic deformation process, namely direct extrusion and variable channel shear deformation (DEVCS), is proposed as a new composite extrusion preparation process for magnesium alloy tubes, which is composed of direct extrusion and unequal channel extrusion. The magnesium alloy tubes with excellent properties can be prepared by DEVCS process. However, the recrystallization behavior and the structure evolution during extrusion are still unclear. In this paper, the forming process of DEVCS was analyzed by DEFORM-3D™ finite element software combined with the metallographic microscope and the electron backscatter diffraction. The results show that the shear deformation in the DEVCS process is conducive to the improvement of strain and strain rate. The high dislocation density in the shear deformation zone promotes the dynamic recrystallization, and the grain size of AZ31 magnesium alloy is improved. In addition, IGMA analysis confirmed that non-basal slip systems were strongly activated during DEVCS process.