The isochronal recovery of irradiation-induced defects was investigated in γ-phase samples (50 or 54at%Al) by means of positron lifetime measurements performed after 2.5MeV electron irradiation at 21K. In the as-irradiated condition, analysis of the results and a comparison with published data, led to a value of 230ps for the lifetime of vacancy-trapped positrons. The lifetime variations which were observed during isochronal annealing at increasing temperatures were consistent with vacancy migration at about 450K. The observation of a progressive decrease in the lifetime of trapped positrons during the migration and elimination of vacancies suggested that they did not form unrelaxed 3-dimensional clusters, and that another type of positron trap was also present.

A Positron Investigation of Electron-Irradiation Induced Defects in γ-TiAl Intermetallic Compounds. G.Sattonnay, C.Dimitrov, C.Corbel, O.Dimitrov: Intermetallics, 1999, 7[1], 23-31