Microstructural and Mechanical Evaluation of Rapidly Solidified Mg–Zn–Ca–Mn and Mg–Zn–Ca–Zr Melt‐Spun Alloys

This work presents the preparation of Mg–2.0Zn–0.5Ca–0.4Mn (CZM) and Mg–1.8Zn–0.3Ca–0.2Zr (CZZ) alloys using typical casting or melt‐spinning, and each followed by hot extrusion. The as‐cast CZM and CZZ alloys comprise well‐formed α‐Mg grains, characterized by numerous coarse Mg ₂ Ca and Mg ₆ Zn ₃ Ca ₂ precipitates, a low solute concentration, and a coarse network of precipitates at the grain boundaries (GBs), together with α‐Mg + Mg ₆ Zn ₃ Ca ₂ and α‐Mg + Mg ₂ Ca eutectic structures at the GBs triple junctions. The as‐cast alloy demonstrates a lower tensile strength (224 MPa) compared to the as‐spun alloy (265 MPa) because of these structural characteristics. In comparison, the microstructure of the as‐spun CZM and CZZ samples is distinguished by coarse grains encircled by relatively fine grains, indicative of dynamic recrystallization. The elevated strength of the as‐spun CZM and CZZ alloys is ascribed to robust refinement of grains strengthening, solution strengthening, and a greater density of smaller precipitates contributing to precipitation strengthening. Fracture study indicates that the as‐cast CZM and CZZ alloys exhibit unique ductile dimples, with quasicleavage and cleavage fractures. The fracture characteristics of the as‐spun CZM and CZZ alloys continue to display cleavage planes and ductile dimples.