From multiscale mechanism to quantitative modelling: Synergistic optimization and defect-property relationships in Mg-10Gd-2Y alloys under pulsed magnetic field

To mitigate the high susceptibility to shrinkage porosity in Mg-10Gd-2Y alloys induced by their wide solidification temperature range, a pulsed magnetic field (PMF) is employed during solidification. By combining multiscale experiments and multiphysics simulations, this study systematically investigates the evolution of electromagnetic and flow fields and quantitatively characterizes the reconstruction of feeding channels within the α-Mg solid skeleton. The results reveal that the synergistic interaction of electromagnetic force, forced convection, and Joule heating not only refines the grains but, more importantly, reconstructs the feeding channels. Quantitative analysis of the three-dimensional network demonstrates that this reconstruction yields a significantly higher channel density, lower tortuosity, and enhanced branching connectivity. Permeability calculations confirm that these structural optimizations enhance liquid-feeding capability, with the improvement scaling positively with the PMF voltage. Consequently, under 150 V, the shrinkage porosity volume fraction decreases by 83.3%, while yield strength, ultimate tensile strength, and elongation increase by 20%, 25%, and 118%, respectively. Furthermore, a quantitative empirical correlation framework is constructed to bridge processing parameters (voltage), 3D defect topologies, and mechanical properties. This model decouples the contributions of shrinkage porosity features, identifying that the reduction of shrinkage porosity size and the optimization of its morphology are the dominant factors driving performance enhancement. Overall, this study creates a closed-loop framework that links external field parameters, microstructural quantization, and performance evaluation, providing both theoretical insight and an analytical framework for manufacturing high-performance magnesium alloy castings.