Dislocation damping and hydrogen pinning in austenitic stainless steels

The room-temperature damping of three Fe-18Cr-Ni alloys was determined as a function of vibrational strain amplitude at 80 kHz. The data are consistent with the Granato-Lücke theory of dislocation damping. Values of Lc (distance between minor pins) measured are consistent with those obtained from a thermodynamic analysis based on Suzuki locking. Hydrogen charging decreases both the damping and modulus defect, indicating that hydrogen pins dislocations in these alloys at room temperature. The pinning corresponds to four hydrogen atoms per 100 lattice atoms along the dislocation, and a hydrogen-dislocation (Hd) binding energy of 0.14 eV. The origin of the Hd interaction lies in the elastic misfit interaction, Suzuki interaction, or combination of both. These estimates of H concentration at dislocations and Hd interaction energy are consistent with the observed release rate of hydrogen from H-charged specimens undergoing plastic deformation.