Vacancies and vacancy clusters were studied, in electron-irradiated or proton-irradiated samples, by means of positron annihilation lifetime spectrometry. No constitutional vacancies were detected in the material. Micro-voids were formed as a secondary defect in electron-irradiated material. This was suggested to be most probably due to dissolving H atoms. All of the constitutional point defects were substitutional antisite atoms. It was found that the irradiated material recovered in 2 main stages. The first stage, at about 250K, was attributed to the migration of Ti vacancies. The second stage, at temperatures above 350K, was attributed to the free migration of vacancies at both sites. Proton irradiation promoted the formation of micro-voids. Electron-irradiated or proton-irradiated specimens recovered almost to the fully annealed state at temperatures below 700K.

Y.Shirai, T.Murakami, N.Ogawa, M.Yamaguchi: Intermetallics, 1996, 4[1], 31-5