Mechanical properties of Mo-Si-B alloys fabricated by using core-shell powder with dispersion of yttria nanoparticles

In recent years, refractory materials with excellent high-temperature properties have been in the spotlight as a next generation’s high-temperature materials. Among these, Mo-Si-B alloys composed of two intermetallic compound phases (Mo₅SiB₂ and Mo₃Si) and a ductile α-Mo phase have shown an outstanding thermal properties. However, due to the brittleness of the intermetallic compound phases, Mo-Si-B alloys were restricted to apply for the structural materials. So, to enhance the mechanical properties of Mo-Si-B alloys, many efforts to add rare-earth oxide particles in the Mo-Si-B alloy were performed to induce the improvement of strength and fracture toughness. In this study, to investigate the effect of adding nano-sized Y₂O₃ particles in Mo-Si-B alloy, a core-shell powder consisting of intermetallic compound phases as the core and nano-sized α-Mo and Y₂O₃ particles surrounding the core was fabricated. Then pressureless sintering was carried out at 1400 °C for 3 h, and the mechanical properties of sintered bodies with different amounts of Y₂O₃ particles were evaluated by Vickers hardness and 3-point bending test. Vickers hardness was improved by dispersed Y₂O₃ particles in the Mo-Si-B alloy. Especially, Mo-3Si-1B-1.5Y₂O₃ alloy had the highest value, 589 Hv. The fracture toughness was measured using Mo-3Si-1B-1.5Y₂O₃ alloy and the value indicated as 13.5 MPa·√m.