Thermal Stability of an Mg‐Nd Alloy Processed by High‐Pressure Torsion.

Abstract

The evolution of microstructure, texture and mechanical properties of an Mg‐1.43Nd (wt.%) alloy are investigated after processing by high‐pressure torsion at room temperature through 5 turns and isochronal annealing for 1 h at 150, 250, 350 and 450 °C using Electron BackScatter Diffraction and Vickers microhardness. The alloy exhibits a good thermal stability up to an annealing at 250 °C, with mean grain size of ≈0.65 μm. The microhardness shows an initial hardening after annealing at 150 °C and then a subsequent softening. The deformation texture, a basal texture shifted 60° away from the shear direction (SD), is retained during annealing up to 250 °C. By contrast, a basal texture with symmetrical splitting towards SD is developed after annealing at 350 °C. The precipitation sequence and their pinning effect are responsible for the age‐hardening, stabilization of grain size and the texture modification. The kinetics of grain growth in the Mg‐1.43Nd alloy follows two stages depending on the temperature annealing range, with an activation energy of ≈26 kJ/mol in the low temperature range of 150–250 °C and ~147 kJ/mol in the high temperature range of 250–450 °C.