Sink strength of grain boundaries for point defects in irradiated ferritic/martensitic steel.

Dislocation-free ferritic/martensitic steel: F82H was prepared by heat-treatment in the appropriate condition in order to investigate the sink strength of grain boundaries for point defects. The size and the areal density of irradiation-induced secondary defects, such as dislocation loops and voids, were investigated in electron-irradiated F82H. The in-situ irradiation experiment resulted in the formation of a defect free zone and the gradient distribution of loop and cavity as a function of distance from boundaries, especially around prior austenite grain boundaries. The atomic density ratio of grain boundary planes is a key parameter in determining the width of defect free zone; a grain boundary with a higher atomic density ratio typically exhibits a wider defect free zone compared to one with a lower ratio. These results clearly indicate that the distribution of irradiation-induced secondary defects in ferritic/martensitic steels is not uniform and is likely controlled by the sink strength, as characterized by the atomic density ratio of grain boundary planes. • Electron irradiation experiment revealed no relationship between the defect free zone (DFZ) widths and misorientation angles of grain boundaries (GBs). • Width of DFZ would be wider at a higher irradiation temperature. • GB character was defined by the atomic density ratio (ADR) of GB planes. And the atomic density of GB plane was defined as (Number of atoms of plane1)/(Unit-area). • GB ADR>>1 showed a wider defect free zone formation compared with GB ADR∼1. • The GB ADR>>1 would be non-equilibrium and has a higher sink strength and a larger strain field compared to the quasi-equilibrium GB ADR∼1. [ABSTRACT FROM AUTHOR]