Influence of extrusion ratio on microstructure and texture developments of high-temperature extruded AZ31 Mg alloy

Abstract

Experiments were conducted to evaluate the effects of extrusion ratio on the microstructure and texture developments of AZ31 Mg alloy during forward extrusion. The forward extrusion was undertaken at 400°C with extrusion ratios of 10, 18, and 25 after the alloy was homogenized at 410°C for 12 h. Partially recrystallized microstructures were observed in all the extruded rods examined. The texture of the large elongated deformed grains appeared strongly centered at $\left\langle {10\bar 10} \right\rangle$ dominating the extrusion texture, while the recrystallized grains exhibited much more randomized texture. For the alloy with the largest ER (25), coarse secondary recrystallized grains were found which presented a different texture component with $\left\langle {11\bar 20} \right\rangle$ parallel to the ED. The occurrence of the coarse secondary recrystallized grains in the alloy with the largest ER might be attributed to that the large ER raised the die exit temperature during extrusion and thus promoted significantly grain growth after the extruded rod exited from extrusion die. The intensities of different texture components varied with ER because ER affected the contents of the deformed grains, DRX grains and coarse secondary recrystallized grains. In particular, the maximum intensity of fiber texture was decreased as ER increased due to the decrease of the large elongated deformed grains.