Tensile properties of multiphase Mo–Si–B refractory alloys at elevated temperatures

Multiphase refractory alloys with nominal composition Mo–9Si–8B–3Hf and Mo–10Si–14B–3Hf (at.%) were produced by a powder metallurgy (PM) technique using elemental powders. These alloys have fine grain sizes and 3-phase, consisting of α-Mo (Mo solid solution) and the intermetallic phases Mo3Si and Mo5SiB2. The tensile properties of these alloys at elevated temperatures were evaluated in vacuum. The Mo–10Si–14B–3Hf alloy has a very good mechanical strength at elevated temperature and displays large tensile ductility. This alloy exhibits a tensile strength of 560 MPa at 1400 °C and a strain rate of 2 × 10−2 s−1. The Mo–9Si–8B–3Hf alloy displays extensive plasticity or superplasticity at temperatures ranging from 1400 to 1560 °C. The tensile elongation of 410% was measured at 1560 °C. Grain boundary sliding is the main mechanism of plastic deformation for these alloys.