STRUCTURE OF OXIDE SCALE OF BINARY TI-AL ALLOYS FORMED IN HIGH-TEMPERATURE AIR

Oxide scale structure of binary Ti-Al alloys containing 20 to 63 mass % Al oxidized in air was studied at 1073 K, 1123 K and 1173 K. As a result, it was observed that for alloys containing less than 51% Al multilayered scale was formed accompanying internal oxidation zone at the base giving smaller oxidation resistance, while for 63% Al alloy oxidation resistant external scale was formed. It was discussed that for the transition from internal to external oxidation in the Ti-Al alloys very high value of critical internal oxide volume fraction was necessary. Also, the internal oxide morphology appeared to influence the structure of the inner scale layer and then the oxidation rate.