Enhanced Strength of We43 Magnesium-Rare Earth Alloy Via Combining Extrusion and Aging

Abstract

In this study, WE43 plates in three states (as-extruded T1, post-aging T5 and solution-aging T6) were prepared by extrusion and heat treatment. The microstructures were characterized by using EBSD, TEM and SEM to reveal the relationship between the microstructure and the mechanical behaviors. The results indicated that both T1 and T5 samples possessed fine grains and precipitates, but the number of precipitates in T5 was higher. The size of precipitates and grains of T6 tended to increase, especially the grain size. The aging treatment could not change the texture distribution of plate, while the solution-aging treatment caused an increase in the texture intensity. The hardness values of the three plates showed an increasing trend: T1< T5< T6. The higher hardness of T5 plate compared to T1 plate was mainly due to the increase in the number of precipitates. The highest hardness of T6 plate 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. T5 plate presented the highest strength thanks to its fine grains and multiple precipitates. The coarse grain size of T6 plate made the crack source tend to initiate at the grain boundary. Its coarse grains were also prone to initiation of twinning, and micro-cracks can be induced near the twin boundaries as well. These result in premature fracture of T6 plates, which in turn led to a serious reduction in plasticity.

Keywords: Rare earth magnesium alloys, aging, Precipitation strengthening, Twinning, Mechanical properties