• • Calcium addition at 1.2 wt.% yields a peak ultimate tensile strength of 380.1 MPa and yield strength of 360.1 MPa with 10.4% elongation, outperforming the Ca-free baseline by a substantial margin, enabling lightweight structural components in aerospace and railway applications where high specific strength is critical.
• • Ignition resistance escalates from 556 °C for ZK60 to 824 °C for the 1.8 wt.% Ca alloy, a 268 °C improvement that directly addresses the spontaneous combustion risk in high-temperature environments, potentially eliminating the need for costly rare-earth additions.
• • The formation of a continuous CaO−MgO oxide layer with PBR values between 1 and 2 ensures protective scaling, as confirmed by the AVR value for CaO/MgO, providing a durable barrier against oxidation during thermal exposure.
• • Microstructural evolution shows that Ca promotes Ca2Mg6Zn3 precipitation while inhibiting MgZn2 in as-cast alloys; after homogenization and extrusion, fragmented Ca2Mg6Zn3 particles and nanoscale MgZn2 precipitates combine with grain refinement to deliver precipitation strengthening and texture effects, achieving a balance of strength and ductility.