Daolun Chen
Vehicle lightweighting is today recognized as one of the predominant approaches to improve fuel efficiency and reduce anthropogenic climate-changing, environment-damaging, costly and human death-causing emissions, since every 10% reduction in weight would lead to about 6~8% increase in fuel efficiency. This, along with materials designed for improved fatigue, creep, impact or corrosion resistance, has been identified as one of six areas critical to solving national and global grand challenges. Magnesium alloy, as an ultra-lightweight metallic structural material, has been increasingly used in the transportation industry to reduce the weight of vehicles. However, the hexagonal close-packed crystal structure of magnesium alloys limits the availability of slip systems and results in strong mechanical anisotropy and tension-compression yield asymmetry due to the presence of twinning and the related development of deformation texture. For the vehicle components subjected to dynamic cyclic loading, such asymmetry could exert an unfavorable influence on the material performance and compromise the structural integrity, safety, and durability of highly loaded structural components. This problem could be overcome through weakening the basal texture via the addition of rare-earth (RE) elements. In this talk a few examples on the deformation behavior of extruded magnesium alloys containing both high and low RE contents will be presented in comparison with RE-free extruded magnesium alloys. Furthermore, twinning and twin growth during uniaxial compression along the extrusion direction and de-twinning along the transverse direction will be discussed as well.
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