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

Abstract

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 (NbSS) phase, while the 3Si and 5Si alloys consisted of NbSS matrix and the eutectic of NbSS plus Nb3Si. After heat treatment, the microstructure contained primary NbSS and NbSS + α-Nb5Si3 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-Nb5Si3 phase improved compressive strength of the NbSS alloy at 1250 and 1350°C, with no degradation in the ductility or formability of the NbSS/Nb5Si3 microstructure. Finally, the failure mechanisms of the NbSS/α-Nb5Si3 microstructure at room and high temperatures were discussed.