Thermal Stability of an Mg–Nd Alloy Processed by High‐Pressure Torsion
Résumé
The evolution of microstructure, texture, and mechanical properties of an Mg-1.43Nd (wt%) alloy is investigated after processing by high-pressure torsion at room temperature through five 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 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. In contrast, a basal texture with symmetrical splitting toward SD is developed after annealing at 350 C. The precipitation sequence and their pinning effects 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 À1 in the low temperature range of 150-250 C and %147 kJ mol À1 in the high temperature range of 250-450 C.
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