HYDROGEN IN IRON

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 and 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 Fe40Ni40P14B6 hydrogen 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.