Fatigue and Deformation of Light Magnesium Alloys

Abstract

Lightweighting has been deemed as one of the most effective strategies to improve fuel efficiency and reduce human-induced emissions in the automotive and aerospace industry. Magnesium alloy, as an ultra-lightweight metallic material, has recently received significant attention in the transportation industry to reduce the vehicle weight due to its high strength-to-weight ratio, dimensional stability, good machinability and recyclability. However, the hexagonal close-packed (hcp) crystal structure of magnesium alloys gives only limited slip systems and develops sharp deformation textures, leading to strong mechanical anisotropy and tension-compression yield asymmetry caused by the presence of twinning in compression and detwinning in tension when loading along the extrusion or rolling direction. For the vehicle components subjected to dynamic loading, such asymmetry could exert an unfavorable effect on the performance. This issue could be overcome through texture weakening via addition of rare-earth (RE) elements and other alloying elements to refine grains and generate nano-sized precipitates. To ensure the structural integrity, durability, and safety of load-bearing structural components, understanding the characteristics and mechanisms of deformation and fatigue of magnesium alloys is vitally important. In this talk, a few examples on the cyclic deformation behavior of extruded magnesium alloys containing both high and low RE contents will be presented in comparison with RE-free extruded magnesium alloys. Moreover, twinning, twin growth, and twin-twin interactions during uniaxial compression in the extrusion direction and de-twinning in the transverse direction will also be discussed.