Enhanced strength of WE43 magnesium-rare earth alloy via combining extrusion and aging

In this study, three types of WE43 plates (as-extruded: T1; Aging after extrusion: T5; Solution-aging after extrusion: T6) were prepared by combining extrusion and heat treatment, and the relationship between their microstructure and mechanical properties was investigated in detail. The results indicated that both T1 and T5 samples possessed fine grains and precipitates, but the number of precipitates in T5 was higher than that of T1. Unlike both of them, the size of precipitates and grains of T6 increased significantly, especially the grain size. In addition, the texture distribution of T5 remained almost unchanged compared to T1, while the texture intensity of T6 showed an increase. The evolution of the microstructure led to an increasing trend in the microhardness values of the three plates, namely: T1< T5< T6. The higher hardness of T5 compared to T1 was mainly due to the increase in the number of precipitates. The highest hardness of T6 was attributed to its coarse grains and extension twinning with high Schmid factor, which increased the probability of twinning, but the contribution of twinning to plasticity was limited. Moreover, the tensile mechanical response showed that T5 presented the highest strength thanks to its fine grains and multiple precipitates, while the T6 exhibited a low ductility, mainly because its coarse grain size made the crack source tend to initiate at the grain boundaries and twin boundaries, resulting in premature fracture.