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Evaluating the textural and mechanical properties of an Mg-Dy alloy processed by high-pressure torsion,

et al.. Microstructure and residual stresses in Ti-6Al-4V alloy pulsed and unpulsed TIG welds. Journal of Materials Processing Technology, Elsevier, 2016, 231, pp.a b s t r a c tIncreasing the pulse frequency in pulsed Tungsten Inert Gas arc welding refines the prior-␤ grain size in the fusion zone of Ti-6Al-4V alloy compared to unpulsed process. The microhardness increases in the fusion zones (FZs) obtained with pulsed welding process with respect to their microstructural evolution. The increase of the pulse frequency contributes to the formation of a significant amount of residual ␤ phase in the FZ which is accompanied by a decrease of its microhardness. The tensile residual stresses (RSs) level in the pulsed process is lower than the one of the unpulsed one. The tensile RSs induced by both welding processes in the heat affected zone (HAZ) are found to decrease when increasing the pulse frequency. In the FZ, the transversal RSs are of compressive type for both processes whereas the longitudinal ones change from tensile to compressive type when increasing the pulse frequency.

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The influence of high-pressure torsion (HPT) processing on the texture and microhardness of two binary Mg-RE (RE=Nd and Ce) alloys was investigated using X-ray diffraction and Vickers microhardness measurements. Disks cut from the alloys were processed by HPT at room temperature for up to 10 turns. The precipitation products of both alloys were identified using synchrotron radiation. The results show that both alloys exhibit a weak basal texture where the c-axis of most grains is shifted 15° from the shear direction. An Mg-1.44Ce (wt. %) alloy showed a continuous decrease in the texture strength which may be due to the effect of second precipitation phases (Mg 17 Ce 2 and MgCe 2). The microhardness of both alloys increased significantly with increasing HPT turns but levelled-off beyond about one HPT turn. Maximum values of ~65 and ~96 Hv were achieved which are significantly higher than the hardness of the undeformed Mg-Ce and Mg-Nd alloys.

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−1 in the low temperature range of 150–250 °C and ≈147 kJ mol−1 in the high temperature range of 250–450 °C.