ANNEALING OF RADIATION-INDUCED DEFECTS IN VANADIUM AND VANADIUM-TITANIUM ALLOYS

The annealing of defects induced by electron irradiation up to a dose of 6 x 10(21) m(-2) at T < 293 K has been investigated in single-cryst als of pure vanadium and in vanadium-titanium alloys with compositions 0.3, 1 and 5 at.% Ti using positron annihilation spectroscopy. The re covery of the positron annihilation parameters in V single-crystals in dicates that the defect annealing takes place in the temperature range 410-470 K without formation of microvoids for the present irradiation conditions. For the alloys the recovery onset is shifted to 460 K, th e width of the annealing stage is gradually broadened with increasing Ti content, and microvoids are formed for annealing temperatures at th e end of the recovery stage. The results show that the vacancy release from vacancy-interstitial impurity pairs and subsequent recombination with interstitial loops is the mechanism of the recovery in pure V. F or V-Ti alloys, vacancy-Ti-interstitial impurity complexes and vacancy -Ti pairs appear to be the defects responsible for the positron trappi ng. The broadening of the recovery stage with increasing Ti content in dicates that solute Ti is a very effective trap for vacancies in V.