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

The microstructure, dynamic recrystallization behavior and texture evolution of an as-extruded Mg-6Zn-1Mn-0.2Gd (ZMG610) alloy at different extrusion conditions (extrusion ratios of 25 and 45, temperatures of 350 and 400 degrees C) were investigated. The as-cast ZMG610 alloy was mainly composed of the alpha-magnesium (alpha-Mg) matrix, the Mg7Zn3 phase and Mg3Zn6Gd (I phase). A large number of I-phase particles remained in the matrix after homogenization treatment at 330 degrees C up to 24 h. The as-extruded ZMG610 alloy exhibited a bimodal structure consisting of fine dynamically recrystallized grains with a wide orientation spread and coarse undynamically recrystallized grains with a strong basal texture. All as-extruded samples exhibited a typical basal texture with the basal plane of most grains parallel to the extrusion direction. A lower texture intensity could be obtained by increasing both the extrusion ratio and temperature. Optimal mechanical properties (yield strength of 267 MPa, ultimate tensile strength of 360 MPa and elongation of 14.2%) were obtained through the combination of a low temperature (350 degrees C) and a high extrusion ratio (45). Amelioration of mechanical properties highly depended on the synergistic effect of dynamically recrystallized grains, I-phase particles and texture.