ANNEALING EXPERIMENTS OF LOW-TEMPERATURE 14 MEV NEUTRON-IRRADIATED ORDERED AND DISORDERED CU3AU BY TEM

Annealing experiments using a liquid-He cryotransfer TEM holder were performed for ordered and disordered Cu3Au irradiated to (5-9)x 10(20) n/m2 with 14 MeV neutrons below 20 K. Almost all TEM-observed defect clusters in a thicker part of disordered Cu3Au were of the interstitial-type, and a significant fraction of those in a thicker part of ordered Cu3Au were expected to be interstitial-type. The mean image diameter of defect clusters in ordered Cu3Au was larger than that in disordered Cu3Au. The possible reason is the lack of long-range focusing along the [110] Cu chains in disordered Cu3Au, which results in a higher cascade temperature and a higher probability of vacancy-interstitial recombination in disordered Cu3Au than in ordered Cu3Au. Because of stage-III annealing, TEM-visible interstitial-type defect clusters started to be annealed out at around 250 K, and superlattice reflections were observed in disordered Cu3Au after room temperature annealing.