Determination of the Nb–Cr–Si phase diagram using diffusion multiples

AbstractA high-efficiency diffusion-multiple approach was employed to determine the phase diagram of the Nb–Cr–Si ternarysystem which is critical for the design of niobium silicide-based in situ composites. These composites have highpotential as a replacement for Ni-base superalloys for jet engine applications. The formation of the Nb(Cr,Si) 2 Lavesphase is beneficial to the high oxidation resistance of the composites and the Nb–Cr–Si system serves as the base forunderstanding the Laves phase formation. The results clearly demonstrate the applicability of the diffusion-multipleapproach in determining such complex phase diagrams as Nb–Cr–Si which contains 14 phases. Two isothermal sectionsat 1000 and 1150 °C were constructed from the results obtained from diffusion multiples using scanning electronmicroscopy (SEM), electron probe microanalysis (EPMA), and electron backscatter diffraction (EBSD). Three ternarycompounds, CrNbSi, (Cr,Nb) 6 Si 5 and (Cr,Nb) 11 Si 8 , were observed at both temperatures, and the C14 Laves phase ofthe Cr–Nb binary system was stabilized by Si to lower temperatures.2003 Published by Elsevier Ltd on behalf of Acta Materialia Inc.