Experimental study of the Fe-Ni-Ti system

In this investigation phase relations in the Fe-Ni-Ti system were studied and two isothermal sections at 800 °C and 1000 °C as well as a revised liquidus projection were established. Microstructural characterisation of the as-cast alloys and of samples equilibrated at 800 and 1000 °C was performed by scanning electron microscopy (SEM), chemical compositions of the phases were analysed by electron probe microanalysis (EPMA), and liquidus temperatures were examined by differential thermal analysis (DTA). The experimental results clarify some uncertainties concerning the melting behaviour and the solid-state phase equilibria between the phases (Ni,Fe)Ti2, (Fe,Ni)Ti and β-Ti. The present data also confirm that the solid solubility of Ti in γ-(Fe,Ni) varies in dependence on the Fe:Ni ratio and decreases with decreasing temperature. The liquidus projection as well as the reaction scheme in the Ti-lean part are modified because two ternaries eutectic E1: L ↔ γ-(Fe,Ni) + Fe2Ti + Ni3Ti and E2: L ↔ Fe2Ti + Ni3Ti + (Fe,Ni)Ti are found at 1108 and 1099 °C, respectively.