Grain Boundary Contributions to Hydrogen-Affected Plasticity in Ni-201
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Hydrogen embrittlement of structural materials, such as nickel-based alloys, is often characterized by enhanced dislocation processes as well as grain boundary decohesion leading to macroscale intergranular fracture. Nanoindentation and scanning probe microscopy (SPM) were used to characterize slip transfer across random grain boundaries and Σ3 recrystallization twins in annealed Ni-201. Thermal hydrogen charging leads to an increase in slip step width within pileups produced by nanoindentation along grain boundaries. The likelihood of slip transmission in the presence of hydrogen depends on the ease of slip within adjacent grains as well as on the misorientation of the grain boundary between them. The observed changes suggest that hydrogen limits dislocation cross-slip while increasing overall dislocation mobility. Coupled nanoindentation and SPM investigations provide a unique, local method for analyzing hydrogen effects on dislocation plasticity, which will be useful in developing grain-boundary-engineered materials.
KeywordsPlastic Zone Hydrogen Embrittlement Intergranular Fracture Hydrogen Charge Slip Step
This work was supported by the Stewardship Science Graduate Fellowship Program under grant number DE-FC52-08NA28752 (to S.K.L.). Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. The authors would like to thank J.A. Campbell for assistance with hydrogen charging.
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