The Fundamentals of Dislocation Transport of Hydrogen in BCC Iron.
CARNEGIE MELLON UNIV PITTSBURGH PA DEPT OF METALLURGICAL ENGINEERING AND MATERIALS SCIENCE
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The detailed characteristics of hydrogen transport by mobile dislocations during plastic deformation in bcc single crystal and polycrystal pure iron has been studied. Single crystals with a proper combination of surface orientation and tensile axis were used to separately study the hydrogen transport rates by screw, edge and mixed dislocations. This study was carried out experimentally through the use of a pair of sophisticated electrochemical cells incorporated with a specially constructed slow strain rate tensile testing device. The experimental uncertainties involved in the measurement of hydrogen flux have also been carefully analyzed and reduced to a minimum, so that the data obtained were able to be accurately interpreted. It was found that qualitatively the hydrogen flux transported by dislocations intimately reflects the dislocation egression on the monitored crystal surface. A competition between hydrogen transport by mobile dislocations and the trapping effect by newly generated sessile dislocations was studied, primarily by using polycrystal iron specimens. Dislocation structures formed with and without the presence of dislocation transported hydrogen in single crystals were also examined by transmission electron microscopy.
- Metallurgy and Metallography