Microstructure Evolution and Deformation Mechanism of Az80 Alloy During Die Forging

Die forging is a processing method that can produce a size and shape close to the finished product and improve the mechanical properties of the alloy. In this paper, Mg-8Al-0.5Zn magnesium alloy was used to prepare stepped shaft by isothermal die forging. The microstructure and stress-strain state of different parts of stepped shaft forging were analyzed. The metal rheological law and microstructure evolution mechanism of AZ80 alloy during die forging were discussed. At the position of low stress and high strain state of the die forging, continuous dynamic recrystallization (CDRX) is the main deformation mechanism, and the microstructure is mainly composed of coarse un-dynamic recrystallization (unDRXed) grains and fine equiaxed dynamic recrystallization (DRXed) grains. The unDRXed grains have a strong [0001] fiber texture, while the DRXed grains exhibit random orientations. At the position of high stress and low strain state of the die forging, {10-12} twinning is the main deformation mechanism, the parent grains show a strong [0001] fiber texture, while {10-12} twins present [-12-10]-[01-10] double fiber texture parallel to forging direction (FD). The compressive strength and yield strength of the part in the low stress and high strain state are higher than those in the high stress and low strain state, but the fracture strain of the former is lower than that of the latter. The results of this study can provide a reference for the design of die forging die together with the blank shape and size, so as to meet the corresponding performance requirements of different parts of the die forging.