Effect of extrusion parameter on microstructure and mechanical properties of Mg-6Zn-1Mn-0.2Gd alloy

Microstructure, dynamic recrystallization (DRX) behavior and texture evolution of as-extruded Mg-6Zn-1Mn-0.2Gd (ZMG610) alloy at different extrusion condition (extrusion ratio of 25 and 45, temperature of 350 °C and 400 °C) were investigated. As-cast ZMG610 alloy was mainly comprised of α-Mg matrix, Mg7Zn3 phase and Mg3Zn6Gd (I-phase), large number of I-phase particles remained in the matrix after homogenization treatment at 330 °C up to 24 h. As-extruded ZMG610 alloy exhibited a bimodal structure consisting of fine dynamically recrystallized grains with wide orientation spread and coarse un-dynamically recrystallized grains with strong basal texture. All as-extruded samples exhibited typical basal texture with basal plane of most grains paralleled to extrusion direction (ED). The lower texture intensity could be obtained through the increase of both extrusion ratio and temperature. Optimal mechanical properties (YS of 267 MPa, UTS of 360 MPa and EL of 14.2%) were obtained through the combination of low temperature (350 °C) and high extrusion ratio (45). Amelioration of mechanical properties highly depended on the synergistic effect of dynamically recrystallized grains, I-phase particles and texture.