Experimental study of the FeAl–NiAl–TiAl section

In this study phase equilibria in the Fe–Ni–Ti–Al system were investigated experimentally, with special emphasis on the FeAl–NiAl–TiAl section. Individual alloys with chemical compositions from this section were prepared by arc-melting in an argon atmosphere, and were examined by differential thermal analysis (DTA). Microstructural characterization of as-cast and samples equilibrated at 800 °C and 1000 °C was performed by scanning electron microscopy (SEM), and the compositions of the coexisting phases were established by electron probe microanalysis (EPMA). The crystal structure of selected alloys was characterized by X-ray diffraction (XRD) and Rietveld refinements. A complete solid solubility of the B2 phase from FeAl to NiAl was observed and the solubility for Ti was seen to decrease with decreasing temperature. The ternary phase Al2FeTi (τ2) also shows a significant extension into the quaternary. In contrast, TiAl has a very low solubility for Fe and Ni.