Positron microbeam evaluation of a stress corrosion crack tip in stainless steels

Yabuuchi, Atsushi; Maekawa, Masaki; Kawasuso, Atsuo

Recently, the SCC propagation model that the vacancy-type defects that accumulate in the crack tip play a role as crack nucleus was proposed. However, there is no information available on the generation or accumulation mechanism of such vacancies around the SCC crack tips. In this study, lattice defect spatial distributions around the SCC crack tip in an austenitic stainless steel have been evaluated probed by positron microbeam. As a result, the increase of S-parameter was observed around the SCC crack. To investigate what type of defect has caused the increase of this S parameter, the -ray energy distribution spectrum obtained from the surrounding of the SCC crack was compared with the spectrum obtained from the tensile test specimen. From the comparison of these two spectra, it can be concluded that the increase of S-parameter near the SCC crack was caused by plastic deformation induced vacancies.