Hydrogen Traps in Cold-Worked Palladium
The enhancement of a phase H solubility in Pd due to the interaction of dissolved H atoms with the stress fields of dislocations was investigated several years ago by one of the authors and his coworkers (1). This phenomenon has been reinvestigated recently by Kircheim (2,3) using an electrochemical technique which allows the monitoring of much lower H contents than the volumetric technique used in the earlier study (1). Solubility enhancements as great as 106 were reported by Kircheim at the lowest H-contents which could be measured. The solubility enhancement is defined as the ratio r′/r where r′ and r are the H-to-Pd atom ratios for a sample with a large dislocation density and for a well-annealed sample, respectively, where both values of r are measured at the same chemical potential of H. Such large solubility enhancements were not found in the original study (1) which was limited to solubilities in excess of r ≃ 10−3. The solubility enhancements were found to be nearly independent of r for r>10−3; this independence is consistent with the theory of the interaction of the elastic fields of edge dislocations with solute atoms (4). The purpose of the present study is to extend the earlier studies (1) using the volumetric technique to the low H content range where the anomalous solubility was noted by Kircheim (2,3).
KeywordsEdge Dislocation Trapping Site Solubility Curve Hydride Phase Trapping Model
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