Investigation of microstructure characteristics of the CVCDEed AZ31 magnesium alloy

In this paper, the mold structure of continuous variable cross-section direct extrusion (CVCDE) was changed by adding interim dies, and the microstructure characteristics of AZ31 magnesium alloy produced by CVCDE with three interim dies were investigated by electron backscattered diffraction (EBSD) and transmission electron microscope (TEM) to study their effects on the mechanical properties. Studies found that the technique of CVCDE with 3 interim dies could effectively refine grains, change texture type and weaken texture intensity, which greatly improved the ductility of AZ31 magnesium alloy. However, compared with the strengthening effect of grain refinement, the weak basal texture and basal slip played a major role on the reduced yield strength. At the same time, the amount of twins reduced and a narrow banded type of extension twin {1012} (86.3° 〈1120〉) occurred after CVCDE with 3 interim dies, which were different from those in original extruded bar.