KINETICS OF DIRECTED OXIDATION OF AL-MG ALLOYS INTO AL2O3 PREFORMS

Synthesis of oxide matrix composites by the directed metal oxidation p rocess offers significant advantages over traditional composite proces sing routes. Much of the previous work on directed oxidation has been focused on the understanding of the microstructural evolution during t he process. In this work, growth kinetics of Al2O3/Al composites throu gh Al2O3 preforms has been studied. The mechanism of oxidation of Al-M g alloys into Al2O3 preforms has been investigated theoretically and e xperimentally. Analysis of the oxidation kinetics for various preform particle sizes and durations of oxidation demonstrates that the prefor m provides preferential sites for Al2O3 nucleation. Furthermore, the w eight gain rate increases with decreasing Al2O3 particle size. With in creasing 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. (C) 1997 Elsevier Science S.A.