Dynamic Compression Behavior of a Mg–Gd-Based Alloy at Elevated Temperature

The dynamic compression behavior and microstructure evolution at 400 °C of an extruded Mg–8Gd–4Y–Nd–Zr alloy with different tempers were investigated. The peak-aged samples exhibit the highest compressive strength, followed by as-extruded samples and over-aged samples. The highest dynamic compressive strength of 582 MPa was achieved by peak-aged sample compressed at 1224 s−1. The high strength was attributed to the formation of abundant thermally stable βʹ precipitates and some dynamic precipitates. The dynamic compressive strength of peak-aged sample and over-aged sample is not sensitive to strain rates, while that of the as-extruded sample is sensitive to strain rates. The dynamic compressive strength of the as-extruded alloy can reach 535 MPa when compressed at 2024 s−1. The high strength was mainly ascribed to the formation of numerous dynamic precipitates and the work hardening effect caused by dislocations. The cracks are composed of crack that is 45° to loading direction on the cylindrical surface and crack on the compressed surface. Microstructure observation indicates that the crack was easily propagated along the interface between the adiabatic shear band and matrix, grain boundaries. The equilibrium phase β in over-aged sample was unable to hinder the crack propagation.