Compressive behaviours of raw and cased porous magnesium-alloys determined by x-ray CT

Abstract

Raw porous magnesium-alloys (Mg-alloys) exhibit lightweight properties and crashworthiness, and are widely used in aerospace and transportation industries. However, they have relatively low strength, and are difficult in controlling dimensional accuracy and surface finish. Cased porous Mg-alloys are therefore a potential solution to overcome these drawbacks. In this study, compression tests and X-ray computed tomography (CT) were performed to acquire mechanical properties and investigate structural deformation/fracture behaviours of the specimens, respectively, under different deformation stages. Results indicated that the raw porous Mg-alloy demonstrated good compressibility. Gradual collapse of the pores led a long plastic plateau stress state, which improved the energy absorption and vibration damping abilities. For the cased porous Mg-alloy, initial cracking of the case was observed at 8.5% strain, whereas the porous structure inside seemed unaffected. This indicated that the solid case acted as a functional layer to provide further protection and decoration of the porous structure. In addition, the yield strength and Young's modulus of the cased porous Mg-alloys are able to be controlled and relatively improved, subjected to the variation in case thickness when compared to the constant values of the raw porous Mg-alloy. Thus, this study leads to a benchmark for further research and development on material deformation and failure models of porous Mg-alloys. Meanwhile, engineers would be able to design and customize the porous structure of Mg-alloys efficiently in potential applications such as protective gears and auto-body structures.