Observation of the crack tip of the stainless steel under the tensile stress probed by a positron microscope

Maekawa, Masaki; Yabuuchi, Atsushi; Kawasuso, Atsuo

For the more detailed evaluation of the interaction between the crack progress by the stress corrosion cracking (SCC) of the stainless steel and the vacancy-type defects, we developed the in-situ measurement method that can measure the distribution of the vacancy-type defects by the positron microbeam under the tensile stress for the continuous corrosion. It was confirmed that the SCC crack progressed when the sample (SUS304, 20 micron thickness, sensitized) was exposed to the corrosion environment (MgCl solution) for 24 hours with the tensile stress of 100 MPa or more. From the observation of the crack tip probed by the positron microbeam, high S-parameter region near the crack tip was detected. This suggests that the vacancy-type defects was introduced along with the crack. In addition, after the more exposure to the erosive environment, the crack progress seems to occur preferentially in the high S-parameter region.