Reaction kinetics of stage III recovery in aluminium after neutron irradiation

Low temperature neutron irradiation of high purity aluminium (up to a dose of 7.2 × 1017 nvt) produces a resistivity change of Δϱ = 5 × 10−8 Ωcm measured at 90.2 °K. The recovery is studied for isochronal and isothermal annealing in the stage III temperature range from 180 to 263 °K. This entire recovery region is uniquely activated with an activation energy of (0.58 ± 0.02) eV. The recovery mechanism is found to be bimolecular, the initial recovery being due to the correlated recovery of defects situated at small relative distances in defect clusters. The last 50% of stage III follow second order kinetics. The capture volume for interstitial‐vacancy recombination can be determined from the measurements. The results support the theory that in stage III interstitial atoms migrate freely and recombine with vacancies.