Microstructure and Oxidation Behaviour of Y-added Mo-Ti-Si-B Alloys

Microstructure and oxidation behaviour of multi-phase Mo-Ti-Si-B alloys with 0.2-1.0 at% Y addition were investigated in this study. In addition to Moss, Ti5Si3, and Mo5SiB2, a Y-rich intermetallic compound, YTiSi, was found to generate in Y-added alloys. With increasing Y-content, microstructure coarsening and increase in Moss volume fraction took place. Y-addition significantly improved the oxidation resistance of the alloys at 800 degrees C due to the formation of a thermally stabilized Y2Mo3O12 layer. However, the positive effect of Y-addition cannot be maintained at 1100 degrees C because of the decomposition of yttrium molybdates during long-term oxidation.