Evaluation of phase relations in the Nb-Cr-Al system at 1000°C using a diffusion-multiple approach

Abstract

A high-efficiency diffusion-multiple approach was used to map most of the phase relations of the Nb-Cr-Al ternary system at 1000°C. This system is very valuable for the design of niobium silicide-based composites. These composites have high potential as a replacement for Ni-base superalloys for jet engine applications. Both Cr and Al are alloying elements for these composites; thus the Nb-Cr-Al phase diagram, especially the stability of the oxidation-resistant Laves phase, is important information for the composite design. A partial 1000°C isothermal section was constructed from the results obtained using electron probe microanalysis (EPMA) and electron backscatter diffraction (EBSD) from a diffusion multiple made up of Nb, Cr, NbAl3, and NbSi2. The stabilization of the C14 Laves phase by Al dominates the 1000°C isothermal section, and the solubility of Al in the C14 Laves phase is as high as ∼45 at.%.