Hot deformation constitutive analysis and processing maps of extruded Mg–Gd binary alloys

Abstract

Hot shear deformation behavior and optimum processing parameters of the binary Mg–xGd (x = 0.5, 1, and 2 wt%) alloys were studied through the development of constitutive equations and processing maps. Shear punch tests (SPT) were performed in the temperature range of 573–723 K and shear strain rate range of 1.7 × 10−2–1.3 × 10−1 s−1. It was observed that increasing the Gd content retarded the dynamic recrystallization (DRX), leading to smaller DRXed grain size, higher amounts of unDRXed elongated patches, as well as higher shear strength. Based on the stress exponent and deformation activation energy values, calculated through constitutive analysis, the dominant controlling mechanisms were suggested as climb-controlled deformation for the Mg–0.5Gd alloy, and dislocation viscous glide for the Mg–1Gd and Mg–2Gd alloys. The processing maps were plotted to obtain the optimum processing conditions for all tested materials. The results show that the temperature of the safe region with maximum efficiency increased by increasing the amount of Gd addition.

Keywords

• Constitutive equation
• Hot deformation
• Mg–Gd alloy
• Processing map
• Shear punch test