Abstract
The effects of minor additions of B on microstructure, ambient tensile strength, fracture toughness and high-temperature oxidation resistance of Nb–Si based alloys were investigated. The added contents were designed as 0.05, 0.10 and 0.20 at.%. The results show constituent phases in 0.05B and 0.20B alloys were Nbss, α-Nb5Si3; while only 0.10B alloy consisted of γ-Nb5Si3. Minor B was prioritized into Nbss and redundant one dissolved into silicide enhanced volume fraction of the silicide. With increasing concentrations of boron, the microstructure was refined at first and then coarsened, while the tensile strength was enhanced remarkably. Compared with other two alloys, the 0.10B alloy containing γ-Nb5Si3 shows both the best fracture toughness and oxidation resistance. The important roles of γ-Nb5Si3 in balancing overall properties are emphasized.
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