This study elucidates the non-thermal mechanism of dislocation density reduction in a Mg-Y-Nd-Gd-Zr alloy under continuous electropulsing (6.67–15 A/mm²) at ultra-low temperatures (−150 °C to −196 °C) through tripartite characterization and first-principles analysis. Electron backscatter diffraction (EBSD) reveals a 15.2 % decrease in geometrically necessary dislocation (GND) density with increasing current, while X-ray line profile analysis (XLPA) confirms the inverse correlation between current intensity and overall defect density. Transmission electron microscopy (TEM) directly visualizes the dissolution of entangled dislocation clusters into isolated lines under high-current treatment (15 A/mm²), corroborating the statistical trends. First-principles calculations demonstrate that localized charge accumulation at defect sites reduces Mg vacancy formation energy by up to 2.8 %, lowering lattice resistance to dislocation glide. This charge-state-dependent vacancy proliferation provides a mechanistic link between electron flow and dislocation annihilation. The reduction of vacancy formation energy is a significant factor in the electron-induced dislocation evolution effect at ultra-low temperatures. These findings provide direct evidence for electron-induced dislocation annihilation mechanisms independent of Joule heating, advancing the understanding of electroplasticity in hexagonal close-packed alloys, and providing a novel approach for rapid, non-oxidative microstructural and property tuning of magnesium alloys.

High thermal conductivity and high strength Mg-1.5Mn-2.5Ce alloy with a tensile yield strength of 387.0 MPa, ultimate tensile strength of 395.8 MPa, and thermal conductivity of 142.1 W/(m·K) was successfully fabricated via hot extrusion. The effects of La and Ce additions on the microstructure, thermal conductivity, and mechanical properties of the Mg-1.5Mn alloy were investigated. The results indicated that both the as-extruded Mg-1.5Mn-2.5La and Mg-1.5Mn-2.5Ce alloys exhibited a bimodal grain structure, with dynamically precipitated nano-scale α-Mn phases. In comparison with La, the addition of Ce enhanced the dynamic precipitation more effectively during hot extrusion, while its influence on promoting the dynamic recrystallization was relatively weaker. The high tensile strength obtained in the as-extruded Mg-1.5Mn-2.5RE alloys can be attributed to the combined influence of the bimodal grain structure (with fine dynamic recrystallized (DRXed) grain size and high proportion of un-dynamic recrystallized (unDRXed) grains), dense nano-scale precipitates, and broken Mg₁₂RE phases, while the remarkable thermal conductivity was due to the precipitation of Mn-rich phases from the Mg matrix.

The addition of effective nucleating particles in the melt to achieve grain refinement has become the most widely used method for the casting industries. In this study, a novel GNP@MgO particle with a nanocomposite structure was prepared by utilizing an in-situ reaction of the carbon source gas with Mg melt. The results showed that the particles can significantly reduce the average grain size of Mg-9Al alloy from 130.4 µm to 13.1 µm, and achieve an ultra-high grain refinement efficiency of 90%. The refinement mechanisms are that the Al₄C₃ phase can act as a heterogeneous nucleation site for α-Mg grains due to the orientation relationship as (001)_Al4C3//(002)_Mg. Meanwhile, the particle distribution model shows that the velocity of MgO particles is much higher than the growth rate of α-Mg grains. Therefore, it is pushed to the vicinity of grain boundaries during solidification, effectively limiting the growth of α-Mg grains. The remarkable grain refinement effect was achieved through the synergistic modulation of Al₄C₃ and MgO particles. This work may provide new insight into designing high efficiency grain refiners for Mg-Al alloys.