脉冲电流作用下纯铁及RPV钢缺陷“修复”的正电子湮没研究

bstract [Background]: 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 RPV steels are a factor of concern, which hinders the life extension of the RPV. Annealing treatment is applied to alleviate irradiation-induced precipitates and defects and recover RPVs 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.[Purpose]: Design and construct a device for EPT processing of samples. The repairs of defects in electron irradiated and deformed iron and RPV steel after EPT has been investigated by using positron lifetime spectroscopy.[Methods]: Electron irradiated pure iron and RPV steel samples were subjected to multi parameter EPT, 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 investigate the relationship between macroscopic properties and microstructure. [Results]: 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. [Conclusions]: The EPT equipment and method used in the experiment can indeed recover the defects of metal samples. The samples treated by EPT are characterized by positron lifetime spectroscopy, and 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 EPTs 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.