Weak-beam TEM study on planar fault energies of Al-lean TiAl-base alloys

Weak-beam transmission electron microscope (TEM) analyses of 1/2〈112〉 superdislocations were performed in order to determine the stacking fault energies in Ti–45Al, Ti–49Al, Ti–45Al–10Nb and Ti–49Al–10Nb alloys (at.%) at 900 °C. In Al-lean binary TiAl alloys, the SISF energies decrease significantly with decreasing Al concentration in the γ phase, from 97 mJ m−2 for 49.6% Al to 64 mJ m−2 for 48% Al. The ternary alloys exhibit a relatively low SISF energy of about 68 mJ m−2, which is practically independent of the Al concentration.