Role of alpha(2)/gamma and gamma/gamma phase boundaries in cavity formation in a TiAl intermetallic compound irradiated with He-ions

A Ti-48at.%Al intermetallic compound has been irradiated with 200 keV Pie-i ons at 623 and 773 K. The helium cavity density decreases with decreasing a lpha (2) and gamma lamella width. A plot of the cavity density and lamella width reveals a linear relationship after irradiation to 15 dpa. Cavity den sity in regions with 300 nm wide lamella is about half of that in large gam ma grains of the specimen. The alpha (2)/gamma lamellar boundaries supply a preferential nucleation site for cavities. Although the cavities are also formed on the gamma/gamma lamellar boundaries, the nucleation is limited to misfit dislocations on the boundaries. Defect-free zones are in the region s of about 50 nm width immediately adjacent to the lamellar boundaries at 7 73 K. These results suggest that the lamellar boundaries are effective sink s for radiation defects and contribute to the suppression of radiation-indu ced defect cluster development in TiAl alloys. (C) 2000 Elsevier Science B. V. All rights reserved.