Microstructure Evolution and Strength–Ductility Synergy of Diffusion-Bonded Rare-Earth Magnesium Alloy Joints Under Electric Current Treatment

Diffusion bonding provides an effective approach for joining rare-earth magnesium alloys; however, achieving a desirable combination of interfacial integrity and ductility in the bonded joints remains challenging. In this work, an electroshock treatment (EST) process has been proposed to improve the microstructure and mechanical properties of diffusion-bonded joints of Mg-Gd-Y-Zn-Zr rare-earth magnesium alloys. Diffusion bonding of the rare-earth magnesium alloy was first performed using an SPS apparatus, followed by EST of the diffusion-bonded joint under varied processing parameters. The experimental results demonstrate that at an EST current density of 50 A/mm2 and a treatment duration of 15 s, the elongation at fracture of the diffusion-bonded joint increases from 2.42% to 3.60%, corresponding to an enhancement of 48.8%, while only a limited change in the ultimate tensile strength is observed. Microstructural characterization indicates local Y enrichment at the diffusion bonding interface. These changes may be associated with the combined influence of Joule heating and possible athermal effects of the applied current; however, their individual contributions cannot be distinguished in the present study. While the electron backscatter diffraction (EBSD) results suggest a redistribution of geometrically necessary dislocations (GNDs) and a tendency toward texture weakening within the analyzed regions. These microstructural changes contribute to the enhanced ductility of the diffusion-bonded joint after EST.