Role of intermetallic nanoparticles in radiation damage of austenitic Fe–Ni-based alloys studied by positron annihilation

The effect of homogeneous distributed nanosized (1–8 nm) intermetallic particles on the evolution of the vacancy defects in fcc Fe–Ni-based alloys during electron irradiation at temperatures 300, 423 and 573 K was studied by the positron annihilation spectroscopy. It was shown that coherent intermetallic nanoparticles like Ni3Al(Ti) inhibited accumulation of the sub-nanometer vacancy clusters. The efficiency of this process depends on type, size and density of nanoparticles and it increases at the elevated irradiation temperatures. It is also observed that in Fe–Ni–Al alloy radiation-induced nucleation of intermetallic particles of Ni3Al type occurs during irradiation at 573 K. In addition, possible mechanisms of the absorption of point defects by nanoparticles are discussed.