Mapping of the Nb–Ti–Si phase diagram using diffusion multiples

A high-efficiency diffusion-multiple approach was employed to map the phase diagram of the Nb–Ti–Si ternary system, which is critical for the design of niobium silicide-based composites. These composites have high potential as a replacement for Ni-base superalloys for jet engine applications. Titanium is one of the most important elements for oxidation resistance and fracture toughness enhancement. Three isothermal sections of Nb–Ti–Si at 1000, 1150 and 1200 °C were constructed from the results obtained from diffusion multiples using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and electron backscatter diffraction (EBSD). Extremely high solubility of Nb in Ti5Si4 (up to ∼46 at.% Nb at 1200 °C, substituting for Ti) was observed.