Effects of intermetallic nanoparticles on the evolution of vacancy defects in electron-irradiated Fe-Ni-Al material

In this paper we study the effects of intermetallic nanoparticles like Ni3Al on the evolution of vacancy defects in the fcc Fe–Ni–Al alloy under electron irradiation using positron annihilation spectroscopy. It was shown that the nanosized (~4.5 nm) intermetallic particles homogeneously distributed in the alloy matrix caused a several-fold decrease in the accumulation of vacancies as compared to their accumulation in the quenched alloy. This effect was enhanced with the irradiation temperature. The irradiation-induced growth of intermetallic nanoparticles was also observed in the pre-quenched Fe–Ni–Al alloy under irradiation at 573 K. Thus, a quantum-dot-like positron state in ultrafine intermetallic particles, which we revealed earlier, provided the control over the evolution of coherent precipitates, along with vacancy defects, during irradiation and annealing. Possible mechanisms of the absorption of point defects by coherent nanoparticles have been discussed too.