DISLOCATION LOOP AND CAVITY FORMATION UNDER HE-ION IRRADIATION IN A TI-RICH TIAL INTERMETALLIC COMPOUND

Damage structure in a Ti-rich TiAl intermetallic compound has been inv estigated by transmission electron microscopy after He-ion irradiation s up to 3 x 10(21) ions/m2 at 623 and 773 K. The irradiations resulted in loop-shaped or dot clusters in the gamma-TiAl and alpha2-Ti3Al gra ins. The cluster density in TiAl was over one order of magnitude lower than that in Ti3Al. The clusters in TiAl irradiated to 3 X 10(21) ion s/m2 at 773 K were identified as interstitial-type faulted loops lying on {111} planes with the Burgers vector direction of [111]. Cavities were created along the grain boundaries as well as in the matrix in Ti Al at 773 K. The EELS analysis indicated that the cavity formation was associated with injected He atoms.