Role of Surface Reactivity in Processing and Performance of Magnesium Alloys

Abstract

The surface reactivity of magnesium alloys at high temperatures required for their processing in solid, semisolid and liquid states is reviewed emphasizing presently existing barriers of its understanding and control. In addition to general aspects of magnesium oxidation, other forms of reactivity such as ignition and flammability are discussed. Since surface oxide, composed of pure MgO, does not offer a sufficient protection, operations of raw alloy melting and component manufacturing require protective atmospheres what has detrimental implications on process economy and product performance. Efforts to develop ignition resistant magnesium alloys through modification of their chemistry are described with a particular role of rare earths and other elements with high affinity to oxygen. It is concluded that all forms of magnesium reactivity in solid and liquid state could be explained through diffusion characteristics of surface oxide formed during processing and service.