Radiation-induced defects in electron-irradiated compounds: the effect of composition

Abstract

The radiation damage produced at 21 K by 2.5 MeV electrons, and the subsequent recovery have been investigated for intermetallic compounds (50 - 54.5 at.% Al) by means of residual electrical resistivity measurements, with particular emphasis on the effects of the composition and fluence. The resistivity damage rate was much higher for the alloys than for a simultaneously irradiated nickel reference sample. Disordering contributes only a small fraction (8 - 15%) to the resistivity damage. The analysis of the dominant defect contribution led to Frenkel-pair resistivity values of , larger than those for pure Al or Ti, and nearly independent of the composition. The recovery of the damage was characterized by two main stages. The temperature of the first one is independent of the composition: it was assigned to close-pair recombination, and to the migration and annihilation of self-interstitials. The second main one (, for the stoichiometric compound) has a temperature which depends on the fluence and on the composition. It corresponds to the migration and elimination of vacancies. An activation enthalpy of was estimated for this stage for stoichiometric TiAl. Its shift to higher temperatures with increasing aluminium content indicates a reduction in the vacancy mobility.

Defects in Metals

“…Relative changes in the defect concentration, for example during irradiation and subsequent annealing, can be monitored precisely, whereas the absolute concentration can be determined only if the magnitude of the specific contribution is known. The method can be applied equally to point defects in pure metals (Lucasson and Walker, 1962), disordered and ordered alloys (Sharma et al, 1978;Vaessen et al, 1984;Karsten et al, 1991;Gilbert et al, 1973;Rivière et al, 1980;Alamo et al, 1986;Dimitrov et al, 1992aDimitrov et al, , 1992bSattonnay et al, 1997). As the contributions from various defects are integrated into a single value, however, discrimination of multiple defect species, if present, is impossible.…”