Kinetics of directed oxidation of Al-Mg alloys into Al₂O₃ preforms

Synthesis of oxide matrix composites by the directed metal oxidation process offers significant advantages over traditional composite processing routes. Much of the previous work on directed oxidation has been focused on the understanding of the microstructural evolution during the process. In this work, growth kinetics of Al₂O₃/Al composites through Al₂O₃ preforms has been studied. The mechanism of oxidation of Al-Mg alloys into Al₂O₃ preforms has been investigated theoretically and experimentally. Analysis of the oxidation kinetics for various preform particle sizes and durations of oxidation demonstrates that the preform provides preferential sites for Al₂O₃ nucleation. Furthermore, the weight gain rate increases with decreasing Al₂O₃ particle size. With increasing oxidation time, liquid metal transport to the oxidation front slows down and becomes a factor in controlling the weight gain rate. The oxidation rate of Al alloys into Al₂O₃ preforms can be tailored by the control of preform particle size.