Microstructure and mechanical properties of titanium aluminide compositions containing Fe

Six titanium aluminide alloys, based on the Ti–Al–Fe system, in the composition space defining the limits of the three-phase (γ+α2+β/B2) field have been prepared. The effects of heat treatment temperature (1000 °C and 1200 °C) and cooling rate (water quenching and air cooling) on the microstructure and room temperature mechanical behaviour (as determined by a shear punch test) are reported. It is shown that additions of Fe between 1.4 at% and 2.8 at% to the binary Ti–44Al alloys may improve room temperature ductility without sacrificing strength. The presence of the disordered bcc phase, rather than the ordered B2 phase, is required to achieve higher room temperature ductility. The preferred microstructure contains β-phase between 15% and 20%, together with a fraction of lamellar (γ+α2) colonies between 30% and 70%. The remainder of the microstructure is γ-phase.