WIT Press

Crystal Plasticity Associated With Crack Stability In Single Crystals


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WIT Press


S. H. Chen, Y. Katz & W. W. Gerberich


A sound physical view regarding quasi crack stability behavior in the sub critical domain remains challenging. As such, it requires exploration and insights into the micromechanical processes of fracture. This study is centered on Fe-3wt % Si single crystals with sub critical crack growth induced by the interactive effects of sustained load and external hydrogen. Pre sharp cracked crystals oriented in both the (001)<010> and (001)<110> directions have been loaded at specific stress intensity factors at 1atm gaseous hydrogen environment that affected dramatically the crack stability. Generally, a fine scale localized approach has been adopted with attention to the crack tip stress field distribution and the tracking of the near fracture surface micro plasticity. In addition the evaluation of the local effective driving force has been attempted. Using an alternative definition, the study is engaged with damage evolution that can be attributed to the dynamic behavior of the crack extension in terms of initiation and the arrest potential. This kind of discontinues behavior still remains in the framework of a global propagation controlled cleavage process. Experimentally, the study was also assisted by the Selected Area Channeling Patterns (SACP) technique that enabled 5┬Ám spatial in a sub micron depth resolution regarding the local strain measurements. The current study emphasized the important role of the dislocation dynamic in semi brittle BCC single crystals. Moreover, it was found that the anisotropic plasticity dominates the near crack tip behavior with implications on the deformation features and thus on the dynamic sub critical crack extension behavior. Keywords: crack stability, single crystal, crystal plasticity, hydrogen effects, sub critical domain.


crack stability, single crystal, crystal plasticity, hydrogen effects, sub critical domain.