| Nowadays, magnesium alloy is the lightest metal as structure material in manyindustries. Magnesium alloy has a wide range of application due to its excellent properties.However, the chemical activity of magnesium alloy is very high. So, magnesium is prone tooxidation and even burning in melting and processing, which greatly induce the efficiencyof magnesium alloy.In this study, alloying method is taken. And appropriate Ca and Ce content are addedinto magnesium alloy, which are considered as ignition-proof elements to improve theignition-proof properties of magnesium alloy. The ignition points of Mg-Ca-Ce alloys aretested. And the mechanism of oxidation is studied from the oxidation film and surfacetension of magnesium alloy melt, the transformation of oxidation film in solid states, thethe oxidation thermodynamics and dynamics of magnesium alloy at high temperature. Theeffect Ca and Ce additions on the microstructure and mechanical properties of magnesiumalloy are also studied.The results of ignition point test show that the ignition point of magnesium alloyincrease with the increase of Ca and Ce content within certain realms. The ignition point ofMg-1.2%Ca-1.2%Ce alloy demonstrate the highest ignition point about780℃, which canmelted at atmosphere without any protection methods.From the EDS, SEM, and XRD analysis, the oxidation film of Mg-1.2%Ca-1.2%Ceis mainly consist of MgO, CaO and Ce2O3, which have a good ignition-proof properties dueto its smooth and compact structure. From the detection of oxidation film cross-section, Caand Ce are mainly exist in the surface of magnesium melt. And the oxidation film ofMg-1.2%Ca-1.2%Ce can divided into three layers. The outer layer is mainly consist ofMgO. The outer layer is mainly consist of composite MgO-CaO structure. The inner layeris mainly consist of composite MgO-Ce2O3structure.The surface tension of magnesium alloy decline with the increasing of Ca and Cecontent. The trend of wrinkles and cracks formation is restrained with the declining ofsurface tension. So the declining of surface tension helps to improve the ignition-proofproperties.Ca and Ce additions are not only improve the ignition-proof properties, but also themicrostructure and mechanical properties within certain realms. The improvement ofstrength and hardness with Ce and Ca additions due to the solid solution strengthening,refined crystalline strengthening and second phase strengthening. |
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