Direct observation of dislocation loops shrinkage upon annealing neutron-irradiated Fe–9Cr alloy

Post-irradiation annealing is an effective way to recover mechanical properties by removing neutron damage. Using in-situ transmission electron microscopy, a neutron irradiated Fe–9Cr alloy was annealed under specific time-temperature scheme. In general, dislocation loops density decreased and their mean size increased upon increasing annealing temperature and time. Concurrent shrinkage phenomenon was observed for both ½<111> and <100> type loops and is found to be vacancy diffusion driven. Essentially, loops’ neighboring microstructure dictates their shrinkage behavior. Shrinkage rate is both loop size and type dependent. Loop size defined vacancy concentration gradient and loop type associated elemental segregation are main deciding factors.