Irradiation-induced vacancy-type defects in the Fe-based dilute binary alloys were studied by positron annihilation, positron lifetime and coincidence Doppler broadening of positron annihilation radiation methods. Vacancy-type defects were introduced by 3MeV electron irradiation at room temperature. The defect concentrations were much higher than that in pure Fe irradiated under the same conditions; thus indicating strong interactions between the vacancies and the solute atoms, and the formation of vacancy-solute complexes. The vacancy-solute complexes in the Fe-Cu, Fe-Ni and Fe-C alloys were definitely identified by using the coincidence Doppler broadening technique. In particular, single vacancies in Fe-Cu were surrounded by Cu atoms; resulting in vacancy-multi-Cu atom complexes of V-Cun (n greater than 6). Vacancy clusters were formed in Fe-Ni and Fe-P, but they were not observed in the other alloys. The isochronal annealing behavior was also studied. Ultrafine Cu precipitates coherent with the Fe matrix were formed in Fe-Cu during annealing at 350C, while the other alloys exhibited complete recovery without forming any precipitate that trapped positrons.

Positron Annihilation Study of Vacancy-Solute Complex Evolution in Fe-Based Alloys. Y.Nagai, K.Takadate, Z.Tang, H.Ohkubo, H.Sunaga, H.Takizawa, M.Hasegawa: Physical Review B, 2003, 67[22], 224202 (6pp)