Dynamic Recrystallization Mechanism and Texture Evolution during Interactive Alternating Extruded Magnesium Alloy

Alternating extrusion (AFE) is a new way to effectively alter the texture and enhance the mechanical properties of the extruded bars. However, the mechanisms of microstructure evolution and enhancement of hardness are still unknown by different extrusion ratios (ERs) during extrusion. This work systematically investigated the microstructure and hardness of AZ31 alloy with various extrusion ratios of 8.1, 15.6, and 24.8 by electron backscattered diffraction. The most striking result to emerge from the data is that when the ERs were increased from 8.1 to 15.6, the grain size was refined to 7.13 μm. However, when the ER reached 24.8, the average grain size was 11.43 μm. The proportion of recrystallization was only 2.92%, there was a continuous rotation of sub-grains at coarse grain boundaries, and non-basal slip < a > dislocations were activated and enriched near low-angle grain boundaries. At present, the recrystallization has not been completed. The grains of the product are coarsened, and the hardness is reduced. When λ = 15.6, the AFE has a significant grain refinement effect and the highest hardness value.