Experimental evaluation of the NbSiTi system from as-cast alloys

Metal-silicon alloys have been extensively studied due to their potential as high temperature structural materials. In this sense, information from accurate phase diagram becomes important. The niobium-silicon-titanium system has been studied experimentally and thermodynamically assessed by different authors, resulting in contradictory isothermal sections and liquidus projections. This work presents results of detailed microstructural characterization of as-cast niobium-silicon-titanium alloys to assess the liquid composition associated to the invariant reactions and of equilibrated samples to determine the 1200 °C isothermal section. Important discrepancies were found between the data obtained in this work and the previous studies of the niobium-silicon-titanium system liquidus projection, especially in the intermediate region. A good agreement between our results and the calculated and experimental isothermal sections proposed in the literature is observed. However, compositional changes are suggested for the location of the observed three-phase equilibria fields.