PSI - Issue 68

Akihiko Fukunaga et al. / Procedia Structural Integrity 68 (2025) 1059–1065 Akihiko Fukunaga / Structural Integrity Procedia 00 (2025) 000–000

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Invers pole figures of the cross-sectional specimen near fracture surface at a strain rate of 7.5 ×10 -6 s -1 are observed by EBSD. In the outer layer, regardless of the crystalline plane, a flat fracture surface, that is, QC fracture surface is formed. The KAM maps of the same area are observed. In the outer layer, unlike the core area, the strain localization along to the fracture surface is observed. This suggests that the plastic deformation was enhanced by hydrogen along to the fracture surface. 3.2. SSRT tests for hydrogen charged A286

Fig.3. (a), (b), (c) Nominal stress − nominal strain curves, (d) Strain dependence of RRA valves, and (e) Fracture surface morphology for SSRT test of 56 ppm hydrogen charged A286 [10].

On the other hand, when the SSRT test was conducted for 56 ppm hydrogen charged specimens or uncharged specimens of A286 at room temperature, the 56 ppm hydrogen charged specimens showed shorter strain and failed near maximum stress, regardless of the strain rate as shown in Figs. 3 (a) − (c). The strain rate dependence of the RRA values was smaller than that in the high pressure gaseous hydrogen as shown in Fig. 3 (d), and facets with slip plane traces were observed as transgranular fracture in each strain rate specimen as shown in Fig. 3 (e). Invers pole figures of the cross-sectional specimen near fracture surface at a strain rate of 7.5 ×10 -6 s -1 are observed by EBSD. The fracture penetrates into the grain, but the direction of fracture is a little shifted at some grain boundaries especially in the center area. KAM maps of same area are observed. There is no difference between KAM map in the core and that in the outer layer, and no strain localization along the fracture surface. This suggests that hydrogen