The effect of hydrogen on dislocation structures around a mixed-mode fatigue crack tip in a single-crystalline iron–silicon alloy was investigated by cross-sectional electron backscatter diffraction and high-voltage electron microscopy. In contrast to the previously reported results in an inert environment, no dislocation cells were formed around the crack tip in a hydrogen environment. The microscopic features around the crack tip suggested that hydrogen promotes a mode I-type crack growth mechanism, which reasonably explains the observed macroscopic crack growth property.

Effect of Hydrogen on Dislocation Structures around a Mixed-Mode Fatigue Crack Tip in a Single-Crystalline Iron–Silicon Alloy. Y.Takahashi, J.Sakamoto, M.Tanaka, K.Higashida, H.Noguchi: Scripta Materialia, 2011, 64[8], 721-4