Improving the exploration of vacancy evolution in P92 alloy under Fe ion irradiation using positron annihilation

P92 alloy, a candidate structural material for supercritical water reactors, was irradiated with 1 MeV Fe ions at 1, 3, and 7 dpa at room temperature, 300, 450, and 550 degrees C. Slow positron beam Doppler broadening spectroscopy was used to characterize the evolution of the open-volume defects. Irradiation of the Fe9Cr alloy at 300 degrees C induced an unexcepted phenomenon in which the S parameter decreased with an increasing irradiation dose; the phenomenon was ascribed to the pinning effect of Cr on dislocation loops, which promoted the recovery of vacancies. Whereas the reduction in the S parameter was generally inhibited in the P92 alloy. These distinctions are related to the evolution of vacancies. We show that the migration of vacancies hindered by C atoms is mainly related to carbon-vacancy complexes in the P92 alloy at approximately 300 degrees C. As the irradiation temperature increased, the complexes gradually dissociated, and the vacancies were captured and annihilated with interstitial atoms. A better understanding of the evolution of vacancies is helpful for investigating irradiation swelling.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

The study investigated the irradiation effects of P92 alloy at different temperatures and doses, revealing the pinning effect of Cr on dislocation loops in Fe9Cr alloy irradiated at 300°C and the hindrance of carbon-vacancy complexes on the reduction of the S parameter in the P92 alloy.