Study On Ignition-proof Mechanisum Of Magnesium Alloy Added With Mischmetal

Magnesium alloys have the advantages of light-weight,high strengthtweight ratio,high stifnesstweight ratio, high damping property and electromagnetism shielding, so it will act animportant role in automobile and electric industry as a weight reducing material.Magnesium is prone to be oxidized during the melting process for its high oxygen afinity,so protective gases of fluxes have to be used as burning prohibitors. However, both protective gases and fluxes would led to the problems such as toxic gas, devices corrosion and alloy properties decent, which prevent the further application of magnesium alloys.In the present dissertation, alloying method was studied to prevent the burning of magnesium alloy during melting. On the surface of the molten alloy, a layer of protective film with dense structure is formed by the addition of mischmetal. The film prevents the penetration of oxygen and volatilization of Mg vapor, and then prevents the magnesium alloy from oxidation and burning.During the experiments, the effects of self-made mischmetal additions on the ignition temperature of AZ91D Mg alloy are investigated. The mechanism of ignition-proof and the effects on mechanical properties are investigated. It is shown, for magnesium alloy with mischmetal in the range of about 1%, that the quality of oxide film is obviously improved, that the ignition temperature point can be greatly heightened.Based on above researches, SEM, XRD and EDS were employed to study the morphology, structure and elements profile of the oxide film growingon the ignition proof magnesium alloy melt, and the results indicated that this oxide film was a kind of film with three-dimensional structure sub-layers. Base on lost of experiment deta, We have analysed the unsuccessful reason of a few misvhmetal or excessive. At last, we have conclude the ignition-proof mechanism and have built the primary oxidating model according to inhered academic knowledge.Lately, other researchers also add pure Ce, mischmetal with rich Ce in magnisium alloy to heighten the ignition temperature, but because the element and the ratio among elements and importing way are different the result is very different. In our experiments, the less quantity was added, and the higher ignition temperature was got. When the highest ignition temperature (823℃)...