Effect of Combined Addition of La and Sm on Mechanical Properties, Microstructure Evolution, and Electrochemical Behavior of Mg-3Zn-1Mn/Sn-0.5Ca Alloy

The effects of the composite addition of La and Sm elements on the microstructural evolution, mechanical properties, and electrochemical behaviors of Mg-3Zn-1Mn/Sn-0.5Ca (wt.%) alloys are systematically investigated. The findings reveal that the Mg-3Zn-1Mn-0.5Ca alloy exhibits excellent ductility, achieving 26% elongation, whereas the Mg-3Zn-1Sn-0.5Ca alloy demonstrates good comprehensive mechanical properties. The addition of La and Sm results in a degree of grain refinement in both alloys and significantly bolsters the strength of the Mg-3Zn-1Mn-0.5Ca alloy, but it has a less pronounced effect on the mechanical properties of the Mg-3Zn-1Sn-0.5Ca alloy. Furthermore, the addition of La-Sm significantly improves the corrosion resistance of both alloys. Electrochemical impedance spectroscopy (EIS) analysis reveals that all four alloys form a double-capacitance loop morphology in 3.5% NaCl, indicating the formation of a protective film during the corrosion process. Among them, the Mg-3Zn-1Mn-0.5Ca-1La-0.5Sm alloy exhibits the largest capacitance loop radius, which is consistent with its polarization curve, indicating the best corrosion resistance. At the corrosion potential of −1.382V, the corrosion current is 8.97 μA·cm−2.