Effect of Aging Treatments on the Nanoprecipitation Mechanism and Dynamic Impact Behavior of Mg-7.5Gd-3Y-0.5Zr Alloy

This study aims to enhance the dynamic impact mechanical properties of Mg-7.5Gd-3Y-0.5Zr alloy by investigating the effects of aging treatments on its microstructure and dynamic impact behavior. Using various techniques, including metallographic observation, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), microhardness testing and split-Hopkinson pressure bar tests, the microstructural and macroscopic static-dynamic properties of the alloy under different aging conditions were thoroughly examined. The findings indicate the following: The aging treatments identified based on hardness curves and TEM analysis include under-aging ([Formula: see text], peak-aging ([Formula: see text] and over-aging ([Formula: see text], with specific conditions of 225[Formula: see text]C for 3[Formula: see text]h, 225[Formula: see text]C for 12[Formula: see text]h and 350[Formula: see text]C for 12[Formula: see text]h, respectively. The alloy exhibits a maximum impact strength of 560 MPa[Formula: see text]under under-aging conditions. Under peak aging, the maximum impact strength increases to 596 MPa. The optimal impact strength under over-aging conditions is 558 MPa[Formula: see text]. The deformation mechanisms of the alloy under under-aging conditions are characterized by a combination of tensile and compressive twinning. In contrast, peak-aging and over-aging conditions primarily involve tensile twinning, with compressive twinning playing a secondary role. The fracture mechanisms of the alloy under various aging states are mainly a mix of ductile and brittle fractures. However, in the under-aged sample, the volume fraction of the dimples is significantly more than that of cleavage planes, which ductile-brittle mixed fracture dominated by ductile fracture; for the peak-aging alloy, the number of cleavage planes increases, showing ductile-brittle mixed fracture dominated by brittle fracture.