Radial Heterogeneity of Microstructure and Mechanical Properties in a Resin Sand-Cast Mg-Gd-Y-Zn-Zr Alloy

This study examines the radial microstructure, texture, tensile properties, and fracture morphology of a 100 mm diameter as-cast Mg-9.5Gd-0.6Y-0.2Zn-0.35Zr (wt.%) alloy prepared by low-pressure resin sand casting. XRD identifies α-Mg as the main resolved phase, while SEM/EDS reveals Zr-rich and Gd/Y-rich particles. The characteristic grain sizes obtained from one EBSD map per region are 88.4, 97.4, and 81.4 μm for the center, near-center, and edge, respectively. Nanoscale features observed by TEM are provisionally associated with β″ (Mg3Gd); their phase identity and strengthening contribution remain unconfirmed. Among the sampled regions, the edge has the highest reported mean ultimate tensile strength (237.0 MPa) and estimated 0.2% offset stress (143.9 MPa). The fracture surfaces predominantly show cleavage-like features. These findings describe the sampled radial locations; local cooling histories and individual strengthening contributions were not quantified.