To investigate the hardening mechanism due to cavity formation in vanadium, in-situ transmission electron microscopy (TEM) observation was performed for the helium ion-irradiated pure vanadium during tensile test. The obstacle barrier strength ¡ was calculated from the bow-out dislocation based on line tension model and the obstacle barrier strength of cavity in pure vanadium was about 0.5 to 0.7 and slightly increased with increasing the cavity size. Generations of cross-slip and double cross-slip occurred with jog generating after the interaction between dislocations and cavities. The fraction of cross-slip and double cross-slip at dislocation pinning were increased with the increasing cavity size and it is suggested that the cross-slip of dislocation can be formed at cavity due to local climb motion of dislocation on the cavity surface.

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The effect of phosphorous on intergranular corrosion of type 310 stainless steel at transpassive potential was investigated using phosphorous added ultra high purity type 310 stainless steel. Intergranular corrosion depth was measured by scanning electron microscopic observation. Grain boundaries were observed using three dimensional atom probe. Intergranular corrosion was observed on phosphorous added stainless steel. The sample heat treated at 600 showed severe integranular corrosion morphology. Observation by three dimensional atom probe revealed that grain boundary with high dissolution rate had segregated zone of chromium and phosphorous about 5nm in width, on the other hand, grain boundary with low dissolution rate had no segregated zone. From these results, it is suggested that intergranular corrosion of phosphorous added type 310 stainless steel at transpassive potential is affected by segregation of phosphorous and chromium along grain boundaries.

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