OXIDATION OF DUCTILE PARTICLE-REINFORCED TI-48AL COMPOSITE

The oxidation behavior of a ductile TiNb particle reinforced Ti-48Al ( at. pet) system was studied at different temperatures. The objective o f this work was to establish the role played by the TiNb reinforcement on the oxidation process. The activation energy for oxidation of Ti-4 8Al was 324 kJ/mol and that of Ti-48Al-20 vol pet TiNb was 315 kJ/mol. The kinetics of oxidation of both the material systems are similar. A t 982 degrees C, the outermost oxide layer in contact with air was alw ays near stoichiometric TiO2. In all the alloys, a layer of porosity w as created just below the outer TiO2 layer by the Kirkendall mechanism as a result of the rapid outward diffusion of Ti atoms. TiNb particle s are more oxidation resistant than Ti-48Al. The boundary of the TiNb particles was oxidized to form TiO2. However, most of the TiNb particl es were untouched and existed as islands embedded within the Ti and Al oxides formed by oxidation of Ti-48Al. Oxidation in pure oxygen lower s the oxidation kinetics, as compared to oxidation in pure air for ide ntical gas flow rates at 982 degrees C.