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 microsc opy, transmission electron microscopy (TEM), and energy dispersive spe ctroscopy (EDS). Iron, Co, Ni, Cr, V, Ti, and Nb were chosen as alloyi ng elements according to the AB(2) structure map or the atomic size fa ctor. The studied MoSi, base alloys were prepared by the are melting p rocess from high-purity metals. The EDS analysis showed that Fe, Co, a nd Ni have no solid solubility in as-cast MoSi, while Cr, V, Ti, and N b 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 ch aracterization indicated that Mo-Si-M-VIII (M-VIII = Fe, Co, Ni) and M o-Si-Cr alloys have a two-phase as-cast microstructure, ie., MoSi2 mat rix 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 C 40 phases, the third phases were observed, which have been identified to be (Mo, V)(5)Si-3, TiSi2, and(Mo, Nb)(5)Si-3.