Microstructural evolution and mechanical behaviour of Nb-10Hf-15W alloy doped with Si

The microstructural evolution and mechanical properties of Nb-10Hf-15W-(0/1/3/5)Si (at.-%) alloys were investigated. The as-cast 0Si and 1Si alloys had a single Nb solid solution (Nb SS ) phase, while the 3Si and 5Si alloys consisted of Nb SS matrix and the eutectic of Nb SS plus Nb 3 Si. After heat treatment, the microstructure contained primary Nb SS and Nb SS + α-Nb 5 Si 3 eutectoid in 3Si and 5Si alloys. Fracture toughness of as-cast and heat-treated samples at room temperature monolithically decreased with increasing Si content. However, the α-Nb 5 Si 3 phase improved compressive strength of the Nb SS alloy at 1250 and 1350°C, with no degradation in the ductility or formability of the Nb SS /Nb 5 Si 3 microstructure. Finally, the failure mechanisms of the Nb SS /α-Nb 5 Si 3 microstructure at room and high temperatures were discussed.