Effect of yttrium, calcium and zirconium on ignition-proof principle and mechanical properties of magnesium alloys

Good ignition-proof principle and mechanical properties were realized in Mg-Y-Ca-Zr alloy system. By adding Y and Ca elements, the ignition point of Mg-3.5Y-0.8Ca alloy was improved to over 1173 K, and the alloy could be melted in air without any protections. The effect of Zr addition on the microstructures and mechanical properties of Mg-3.5Y-0.8Ca alloys were investigated, and Mg-3.5%Y- 0.8%Ca-0.4%Zr alloy had good comprehensive properties with tensile strength of 190 MPa and elongation of 11%. Auger electron spectroscopy (AES) and X-ray diffraction (XRD) analysis revealed that the oxide film formed on the surface of Mg-3.5Y-0.8Ca alloy was mainly composed of Y2O3. Thermogravimetric measurements in dry air indicated that the oxidation dynamics curves measured at 773, 873 and 973 K followed the cubic law. Moreover, the semiconductor characteristic of Y2O3 film and its effect on ignition-proof properties of Magnesium alloys were discussed from the viewpoint of electrochemistry.