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.