The defects generated during the working process of metal materials have a significant impact on their performance. For example, the radiation-induced embrittlement and hardening of reactor pressure vessel (RPV) steels are a factor of concern, which hinders the life extension of the RPV. Annealing treatment is applied to alleviating irradiation-induced precipitates and defects and recover RPV's mechanical properties in the past few decades to extend the in-service lifetime of the RPV. Unfortunately, this conventional method generally requires a high treatment temperature and long operation time, inevitably wasting considerable energy due to the huge size of the RPV. Recently, as a more convenient and energy-saving method, the repair of metal defects by electropulsing treatment (EPT) has been developed.

This study aims to design and construct a device for EPT processing of samples, and investigate the repairs of defects in electron irradiated and deformed iron and RPV steel after EPT by using positron lifetime spectroscopy.

Electron irradiated pure iron and RPV steel samples were prepared and subjected to multi parameter EPT device developed in laboratory, and the changes in defects of the samples with EPT were characterized by positron lifetime spectroscopy. In addition, the mechanical properties of pure iron tensile samples were characterized by micro Vickers hardness, and the defect information was characterized by positron lifetime spectroscopy to explore the relationship between macroscopic properties and microstructure.

The defects introduced by electron irradiation in pure iron and RPV steel samples gradually recover after EPT and exhibit similar patterns to annealing treatment. After stretching, the number of defects in pure iron samples increases, leading to an increase in Vickers hardness. EPT can restore defect and reduce Vickers hardness.

The defects generated by irradiation or deformation in pure iron and RPV steel can be partially repaired through EPT. The effect of defect repair is not only related to the initial state of the sample, but also to EPT's parameters. As a new non-destructive testing method, positron annihilation is expected to provide a criterion for material damage or defect repair under the action of pulse current, which can conveniently, quickly, and sensitively detect the defect state of actual working components.