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Then the sample was tilted for detailed observation of the stress corrosion cracks on the electropolished side. As shown in Fig. 13, there were three kinds of structure at the edge at locations D and E. These indicate that intergranular stress corrosion cracks formed on this surface during the LIST test. During the overload, the fracture propagated first in a tearing mode, then by microvoid coalescence to produce the dimple areas that made up most of the fracture surface. The detailed observations of the opened IG cracks, as shown in Fig. 13, indicate that the electropolished surface was covered by an oxide film. This oxide film grew to a thickness of several microns during the LIST test, and is clearly visible in sections of LIST samples (e.g. Figs. 10 and 11). At the opened cracks, there was a narrow region of intergranular stress corrosion cracking. Following this IGSCC, there was a tearing structure (which was also present in JQ1, the service crack in segment A1, and also in a LIST sample fractured in air). The tearing structure was followed by dimple fracture.