Local and Long‐Range Diffusion of Hydrogen in Amorphous and Partially Crystallized Fe 90 Zr 10 Alloys

The magnetic after‐effect spectra of hydrogen (H) charged amorphous Fe 90 Zr 10 alloys containing different degrees of crystallization (10% and 50%) are measured in the temperature range between 4.2 and 480 K. For the partially crystallized specimens one broadened asymmetric relaxation maximum is observed. With decreasing H content a shift of the maximum temperature from 140 to 196 K takes place due to the increase of the average activation enthalpy from 0.33 up to 0.49 eV. Using a phenomenological diffusion model for H in amorphous alloys, which takes into account a broad distribution of equilibrium sites as well as of saddle point energies the H‐induced relaxation maxima and their annealing behaviour are assigned to local jumps of hydrogen in the amorphous phase. In addition, the long‐range H diffusion above 300 K is measured by thermal degassing at different heating rates. The observed similar H degassing kinetics of the amorphous and partially crystallized samples show that the long‐range diffusion is exclusively determined by H atoms in the amorphous phase. The average activation parameters Q diff = (0.53 ± 0.1) eV and D o = 7 × 10 −7±2 m 2 /s are evaluated for a H concentration of 1.7 at%.