Recovery of the quenched-in solute hydrogen atoms in nickel

The recovery process of hydrogen dissolved in excess in nickel is studied by means of the liquid hydrogen quenching method which is a modified Schultz's method. A recovery stage of electrical resistance is found in the range 190K--380K in the isochronal annealing curves. It is found that during the annealing the dissolved hydrogen atoms diffuse to and escape out of the surface of the specimen producing the timewise and spacewise varying distribution of concentration in the interior. The resistance of the specimen is calculated by using an equivalent circuit of the parallel connection of concentric hollow cylinders having different values of electrical resistivity depending on the hydrogen concentration which can be obtained from the diffusion equation. Extremely good agreement is obtained between the experiment and calculation, and the diffusion coefficient is determined as D=2.14x10-3 exp(-8880/RT) cm2/sec. (auth.)