High strain-rate behavior and deformation mechanism of a multi-layer composite textured AZ31B Mg alloy plate

Abstract

There are currently very few studies on the high strain-rate properties of Mg alloys with multi-layer composite textures under dynamic loading. In present study, a multi-layer composite textured AZ31B Mg alloy plate was fabricated using the asymmetric twin-roll casting process. The high strain-rate (∼103 s−1) deformation behaviors of the AZ31B plate along the normal direction (ND) were investigated using split-Hopkinson pressure bar technique. The microstructural evolution and deformation mechanism were analyzed by optical microscopy, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy methods. The experimental results show that the mechanical behaviors exhibit a power-law hardening response under high strain-rate deformation. The flow stress generally increases with increasing strain rate, whereas the strain-hardening rate decreases with increasing strain. An interesting feature is that the maximum flow stress at high strain rates is much lower than that at its corresponding quasi-static counterpart. Microstructure analysis demonstrates that the characteristic layered texture and microstructure along the ND determine its mechanical behavior. The plastic deformation is mainly controlled by the basal-type texture, where the predominant deformation mechanism is dislocation slip. Dynamic recrystallization (DRX) occurred unevenly in the material during dynamic deformation, resulting in a moderate increase in ductility. The fracture behaviors change from brittle fracture to ductile fracture as the strain rate increases. The energy absorption capacity is therefore enhanced due to the occurrence of both DRX and the brittle–ductile transition at high strain rates.