Decomposition and reaction of thermal-formed alumina in aluminum alloy castings

Oxide films are readily entrapped in aluminum alloy castings during the melting, pouring or filling process resulting in defective geometry or quality. The entrapped oxide films may be of different shapes and/or composed of varying constituents (or oxides). It is extremely difficult to directly produce a given type of oxide film with a given thickness, from the aluminum alloy melt. Aluminum alloy castings have a thermally formed aluminum oxide film on their machined surface after being heated. In this study thermally formed aluminum oxide samples were produced from pure aluminum. The intend is to investigate the reaction and decomposition of this oxide in aluminum alloy melts. The reactions of the thermally formed aluminum oxide with aluminum-silicon and aluminum-magnesium alloys are discussed.