This article describes the phase stability, microstructures and mechanical properties of silicide-reinforced Nb alloys in Nb-Mo-W-Si quaternary system prepared by arc melting and heat treatment. There exists an equilibrium two-phase field of Nb solid solution (Nbss) and α(Nb,Mo,W)5Si3 in a Nb-rich region of this quaternary system. Alloys in this region have a eutectic reaction of L → Nbss+β(Nb,Mo,W)5Si3 during solidification. The β(Nb,Mo,W)5Si3 transforms to the stable α(Nb,Mo,W)5Si3 at very high temperature. The cast and heat treated hypoeutectic alloys consist of dendritic Nbss, network-shaped Nbss matrix and α(Nb,Mo,W)5Si3. These quaternary alloys exhibit excellent high-temperature strength, although the fracture toughness is still unacceptable for practical applications.
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This research is supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.
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Ma, C., Tan, Y., Tanaka, H. et al. Microstructures and High-temperature Strength of Silicide-reinforced Nb Alloys. MRS Online Proceedings Library 646, 395–400 (2000). https://doi.org/10.1557/PROC-646-N5.39.1