Abstract:To address the challenge of synergistically improving the strength and corrosion resistance of magnesium alloys, the effects of extrusion temperatures (360 °C and 380 °C) on the microstructure, mechanical properties, and corrosion behavior of the Mg-2Zn-0.8Mn-0.7Gd-0.3Ca alloy were systematically investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscattered diffraction (EBSD), scanning Kelvin probe force microscopy (SKPFM), tensile tests, immersion tests, and electrochemical measurements. The results show that the most significant microstructural effect of increasing the extrusion temperature to 380 °C is the remarkable promotion of dynamic precipitation of α-Mn nanoparticles. These precipitated phases pin the grain boundaries and inhibit grain growth. Through the combined effects of second-phase strengthening and grain refinement strengthening, the yield strength of the alloy is increased from 202 MPa to 244 MPa. Meanwhile, after stable immersion in 3.5 wt% NaCl solution, the surface film resistance of the alloy is enhanced from 2238 ohm cm2 to 4811 ohm cm2, and the corrosion rate is reduced from 1.325 mm·y-1 to 0.839 mm·y-1. The improved protective performance of the film may be associated with the precipitation of dispersed nano-sized α-Mn particles. By simply adjusting the hot extrusion process, this study achieves the simultaneous enhancement of strength and corrosion resistance, providing a new perspective for the design of high-strength and corrosion-resistant magnesium alloys.