Ternary alloying study of MoSi2

Ternary alloying of MoSi2 with adding a series of transition elements was investigated by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS). Iron, Co, Ni, Cr, V, Ti, and Nb were chosen as alloying elements according to the AB(2) structure map or the atomic size factor. The studied MoSi, base alloys were prepared by the are melting process from high-purity metals. The EDS analysis showed that Fe, Co, and Ni have no solid solubility in as-cast MoSi, while Cr, V, Ti, and Nb exhibit limited solid solubilities, which were determined to be 1.4 +/- 0.7, 1.4 +/- 0.4, 0.4 +/- 0.1, and 0.8 +/- 0.1. Microstructural characterization indicated that Mo-Si-M-VIII (M-VIII = Fe, Co, Ni) and Mo-Si-Cr alloys have a two-phase as-cast microstructure, ie., MoSi2 matrix and the second-phase FeSi2, CoSi, NiSi2, and CrSi2, respectively. In as-cast Mo-Si-V, Mo-Si-Ti, and Mo-Si-Nb alloys, besides MoSi2 and C40 phases, the third phases were observed, which have been identified to be (Mo, V)(5)Si-3, TiSi2, and(Mo, Nb)(5)Si-3.