The clustering of vacancies in severely quenched solid-solution alloys, with Li contents of between 230 and 2760ppm, was studied by means of Doppler broadening spectroscopy. The samples were initially annealed (873K) in dry air or pure dry N. The onset temperature for vacancy clustering in samples which had initially been annealed in air was found to be 150K. This was 40K lower than that for N-annealed samples. This result was consistent with the migration of divacancies which formed as a result of the appreciable increase in vacancy concentration that was caused by Li migration to, and oxidation at, the surfaces of samples which were annealed in air. The Li-vacancy binding was also suggested to contribute, to a lesser extent, to the retardation of vacancy migration in the N-annealed samples. No dependence upon Li content was detected; thus indicating a saturation of the positron response to vacancy-type defects in each case.

Vacancy Clustering in Quenched Al-Li Solid-Solution Alloys Studied by Doppler Broadening Spectroscopy. H.P.Leighly, P.G.Coleman: Journal of Physics - Condensed Matter, 1998, 10[46], 10423-8