ELUCIDATING THE MECHANISTIC INFLUENCE OF STRENGTHENING PRECIPITATE MORPHOLOGY ON HYDROGEN ENVIRONMENT-ASSISTED CRACKING IN A NI-CU SUPERALLOY

摘要

Recent studies on Ni and Fe-based alloys utilizing transmission electron microscopy (TEM) of the near-fracture surface region have revealed a systematic refinement in the dislocation cell structure of hydrogen-charged specimens relative to non-charged specimens. These observations suggest that hydrogen-induced localization of deformation may provide an important contribution to the microscale processes by which hydrogen degrades the performance of structural metals. Moreover, this finding implies that microstructural features which affect deformation processes could be tuned so as to increase an alloy's intrinsic resistance to hydrogen-induced degradation. For example, given the dominant influence of strengthening precipitates on deformation processes in precipitation-hardened alloys, it is hypothesized that such particles could be optimized to mitigate this hydrogen-induced localized deformation. However, studies which evaluate the role of precipitate morphology on these localized deformation processes in the context of hydrogen-induced cracking are limited in number and often complicated by the simultaneous influence of other microstructural features.