Influence of solid-solution processes on the microstructure and dynamic impact behavior of cast Mg-Gd-Y-based alloys

Abstract

This research explores the influence of solid solution treatments on the microstructural characteristics and dynamic impact behavior of Mg-Gd-Y-Zr alloys. A comprehensive analysis of microstructural evolution under various solution treatment conditions was conducted using metallographic observation, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). The mechanical response of the alloys under dynamic loading was assessed via impact testing using a split-Hopkinson pressure bar (SHPB).The results reveal that the most effective single-stage treatment occurs at 520 °C for 6 h, yielding an average grain size of approximately 50.6 μm. In contrast, the optimal two-stage solution treatment involves an initial annealing at 350 °C for 6 h, followed by heating at 520 °C for 1 h, leading to a refined grain structure with an average size of 46.8 μm. Both treatment methods significantly enhance impact resistance. Under a strain rate of 4000 s⁻¹, the single-stage treated alloy attains a peak compressive strength of 512 MPa, which is attributed to the synergistic effects of dynamic precipitate formation and the presence of coarse rare-earth-rich particles. Meanwhile, the two-stage treated alloy exhibits a superior maximum compressive strength of 540 MPa, primarily due to grain refinement and alterations in the composition of rare-earth hydride particles, which contribute to enhanced deformation resistance.