(The) effects of vacancy on hydrogen diffusivity and solubility in pure iron at room temperature

Abstract

This work examined the role of lattice vacancies in hydrogen diffusion in electrolytic iron by using an electrochemical permeation technique. Isothermal annealing at $80\,^\circ\!C$ was conducted to remove only vacancies for the quenched specimens, and electrical resistivity was measured for various annealing times. The coldworked specimens were annealed at $150\,^\circ\!C$ for 24 hours to remove vacancies and $600\,^\circ\!C$ for 5 hours to eliminate dislocations. For both the specimens, the values of diffusivity were found to increase as vacancies were annealed out. The values of solubility and electrical resistivity were contrary to the results of diffusivity. The interaction energies of hydrogen with lattice vacancy and dislocation for pure iron at $7\,^\circ-40\,^\circ\!C$ were found to be 50.7 KJ/mol and 50 KJ/mol, respectively indicating that influence of lattice vacancy on hydrogen diffusion can not be neglected.