Effect of extrusion temperature on the dynamic recrystallization behavior and mechanical properties of flame-retardant Mg-4Y-2Nd-1Gd-0.5Zr-1Ca alloy

This study investigates the effects of extrusion temperature (440 °C, 470 °C, and 500 °C) on the dynamic recrystallization (DRX) mechanism and mechanical properties of Mg-4Y-2Nd-1Gd-0.5Zr-1Ca alloy. Specifically, continuous dynamic recrystallization (CDRX) dominates the DRX process at 440 °C and 470 °C, whereas discontinuous dynamic recrystallization (DDRX) becomes the primary mechanism at 500 °C. Particle-stimulated nucleation (PSN) is operative at all temperatures. The alloy strength increases slightly with rising extrusion temperature. The alloy extruded at 500 °C exhibits the optimal comprehensive mechanical properties, with ultimate tensile strength, yield strength, and elongation reaching 221 MPa, 165 MPa, and 8.5%, respectively. Flame-retardant testing reveals no combustion at 900 °C, as the dense composite oxide film consisting primarily of CaO and Y 2 O 3 forms on the alloy surface. After aging at 225 °C for 14 h, finely dispersed second-phase particles precipitate within the grains, elevating the ultimate tensile strength and yield strength to 239 MPa and 203 MPa. This study provides a theoretical basis for process optimization of high-performance flame-retardant magnesium alloys.