Elastic Property Dependence on Mobile and Trapped Hydrogen in Ni-201
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Enhanced dislocation processes can accompany decohesion mechanisms during hydrogen degradation of ductile structural metals. However, hydrogen–deformation interactions and the role of defects in degradation processes remain poorly understood. In the current study, nanoindentation within specifically oriented grains in as-received, hydrogen-charged, aged, and hydrogen re-charged conditions revealed a “hysteresis” of indentation modulus, while the indentation hardness varied minimally. Thermal pre-charging with approximately 2000 appm hydrogen decreases the indentation modulus by ~20%, aging leads to a slight recovery, but re-charging drives the modulus back down to values similar to those measured in the hydrogen-charged condition. This “hysteresis” indicates that dissolved interstitial hydrogen is not solely responsible for mechanical property alterations; hydrogen trapped at defects also contributes to elastic property variation.
This work was supported by the DOE NNSA Stewardship Science Graduate Fellowship [Grant DE-NA0002135] (SKL) and the Laboratory Directed Research and Development program at Sandia National Laboratories [Grant SNL-LDRD-173116], a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.