Hydrogen in iron
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Hydrogen in Iron
HERBERT H. JOHNSON
The applicability of advanced permeation techniques to the study of hydrogen and deuterium in iron and iron alloys is described. Time lag measurements lead to detailed information about hydrogen transport processes, including lattice diffusivities and trap binding energies and densities. The experimental technique couples gas phase charging of palladium coated specimens with the sensitive electrochemical detection method. In both annealed and deformed iron the trap binding energy for hydrogen and deuterium is 50 to 58 kJ/mol, while the trap density varies from about 1020 m -3 for annealed iron to over 1023 m -3 for heavily deformed iron. For the metallic glass Fe40Ni4oPl4B6hydrogen transport occurs between energetically equivalent sites, with no evidence of trapping. The site density was estimated as about 6 • 1029 m--3 . The hydrogen concentrations studied were several orders of magnitude less. Hydrogen and deuterium in iron differs only in their lattice diffusivities. The diffusivity ratio conforms nearly to the classical inverse square root of mass ratio, but shows a slight temperature dependence. The solubilities, trap binding energies, and partial atomic volumes of the two isotopes in iron are identical.
The Edward DeMille Campbell Memorial Lecture was established in 1926 as an annual lecture in memory of and in recognition of the outstanding scientific contributions to the metallurgical profession by a distinguished educator who was blind for all but two years of his professional life. It recognizes demonstrated ability in metallurgical science and engineering. HERBERT H. JOHNSON is Professor of Materials Science and Engineering at Cornell University. He received his B.S. in Physics from Case Institute of Technology as well as the M.S. and Ph.D. in Physical Metallurgy. He began his academic teaching career at Lehigh University in 1957, later became a member of the faculty at Cornell University in 1960, and was Visiting Professor at Massachusetts Institute of Technology in 1967-68. From 1970 to 1974 he served as Director of the Department of Materials Science and Engineering at Cornell and from 1974 to 1984, he was the Director of the Materials Science Center at Cornell University. His major research interests center around hydrogen in metals, phase stability, thermodynamics of solids, and corrosion. His contributions to the METALLURGICALTRANSACTIONS B
scientific community have been recognized by various awards and honors, including membership in the National Academy of Engineering and selection as a Fellow of the ASM INTERNATIONAL, delivering the Keynote Lecture at the Alexander R. Troiano Memorial Symposium in 1980, holding the Citation Index Award for "one of the most cited items in its field" in 1982, and being frequently invited as a lecturer at national and international meetings. His present major professional activities involve being a member of the Solid State Science Committee of the National Research Council (Chairperson designated for 1987-89); the Council on
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