Effect of extrusion conditions on microstructural characteristics and mechanical properties of SEN6 magnesium alloy

Abstract

This study investigates the influence of extrusion conditions on the microstructure and tensile properties of Mg–6Al–0.3Mn–0.3Ca–0.2Y (SEN6) alloy, which is processed at various extrusion temperatures and ratios. An increase in both the extrusion temperature and ratio facilitates dynamic recrystallization during hot extrusion by enhancing thermal and strain energies, increasing the area fraction of recrystallized grains within the extruded material. As either the extrusion temperature or ratio increases, lattice rotation within the recrystallized grains intensifies, resulting in a stronger basal texture in the extruded material. During extrusion, the undissolved Al2Y, Al8Mn4Y, and Al2Ca particles within the billets are partially fragmented and realigned along the extrusion direction. However, the quantity, size, and dispersion of these particles are largely unaffected by variations in extrusion temperature and ratio. The tensile yield strength of the extruded material shows a positive correlation with increasing extrusion temperature and ratio, predominantly due to enhanced texture hardening. Specifically, the tensile yield strength of the material extruded at 400 °C with an extrusion ratio of 25 is 23.2 MPa higher than that of the material extruded at 300 °C with an extrusion ratio of 10. Despite the presence of non-recrystallized grains in materials extruded at the lower extrusion ratio of 10, compression and double twins form uniformly throughout the material during tension, as the widths of non-recrystallized grains are similar to those of recrystallized grains. Consequently, all extruded materials exhibit high tensile elongations, exceeding 20%.