The origin of a new phase observed during quenching of a TiAl-2Fe alloy

Microstructure formation in the Ti–49.6at.% Al–1.9at.% Fe alloy after fast and slow cooling from 1200°C was examined and analyzed by X-ray diffraction, scanning and transmission electron microscopy combined with electron probe microanalysis. Formation of a previously unidentified τ′2 phase is reported and discussed. It has a tetragonal lattice with lattice parameters a=11.5 Å, c=13.8 Å. Possible orientation relationships between the τ′2 phase and the parent FeTi(Al) are [010]τ′2 ∣∣ [001]FeTi(Al) [100]τ′2 ∣∣ [110]FeTi(Al) and [001]τ′2 ∣∣ [1̄10]FeTi(Al).