Microstructure, mechanical properties and oxidation resistance of Mo5Si3-Al2O3 composite

Mo5Si3-Al2O3 composite powders were successfully synthesized by ball milling MoO3, Mo, Si and Al powders. A dense nanostructure Mo5Si3-Al2O3 composite was consolidated by hot pressing sintering. Microstructure, mechanical properties and oxidation resistance of Mo5Si3-Al2O3 composite were investigated. Results showed that Mo5Si3-Al2O3 composite has good mechanical properties and oxidation resistance compared with Mo5Si3 alloy. Mo5Si3-Al2O3 composite with a relative density of 96.1% and the average grain size was approximately 1-3 μm. The hardness, flexure strength and fracture toughness of Mo5Si3-Al2O3 composite are 15.2 GPa, 630 MPa and 6.53 MPa m1/2, respectively. Meanwhile, the composite has higher strength (~276 MPa) at 1400 °C. The oxidation test at 600 °C showed that the addition of Al2O3 effectively restrained the pest oxidation of Mo5Si3. The oxide scale consists of SiO2-Al2O3 was formed on the surface of Mo5Si3-Al2O3 composite at 1200 °C, and the SiO2-Al2O3 film presents good oxidation resistance compared to the pure SiO2 film.