Unveiling mechanical response and deformation mechanism of extruded WE43 magnesium alloy under high-speed impact

To clarify the mechanical behavior and deformation mechanism of rare earth magnesium (Mg) alloy WE43 under extreme service loads, high-speed impact tests under various deformation temperatures and loading paths were conducted using a split Hopkinson pressure bar. The flow stress along extrusion direction (ED) and extrusion radial direction (ERD) decreases apparently with deformation temperature. Compared with conventional Mg alloys, it exhibits a slight anisotropy and an unusual C-shaped characteristic. Cellular dislocation, mechanical twin and fine grain that occur after high-speed impact deformation are insensitive to the loading direction, but strongly dependent on the deformation temperature, especially superimposed with adiabatic temperature rise. As a result, dynamic recrystallization (DRX) occurs even at an ambient temperature of 25 °C. Double twinning and prismatic slip or pyramidal slip are the dominant deformation mechanisms at 25 °C. These twins induce mechanical cutting refinement to form some fine-grained structures, accompanied by a small number of fine grains by twinning induced DRX. In contrast, the deformation at 250 °C is mainly controlled by prismatic slip and pyramidal slip, accompanied by various types of twinning in early deformation stage. Compared with 25 °C, more fine-grained microstructures are formed at 150 and 250 °C through a synergy mechanism of twinning induced mechanical cutting and twinning induced DRX.