Ultrasonic investigation of the interaction of hydrogen-dislocations in copper crystals

In this paper we present experimental data of ultrasonic velocity and attenuation obtained in a high purity crystalline sample of copper hydrogenated by gaseous charge. The sample is oriented in the 〈1 1 1〉 crystallographic direction and aged for this work in three stages between 64 and 97 days. The results indicate that the hydrogen is mainly segregated at the dislocation core, inhibiting the hydrogen Snoek–Köster relaxations verified at earlier ageing stages. Despite this, a contribution to viscosity in the kink-chain resonance is provided by the mobile hydrogen in the dislocation core by its side movement along the dislocation line. At temperatures at which the hydrogen begins to freeze in the lattice the geometrical kinks find a gradual increase on the hindering of their movements along dislocation lines, becoming immobile when the hydrogen is completely frozen in the crystal, anchoring the dislocations in short loops. Although the viscosity associated with the mobile hydrogen is removed, the resonance associated with geometrical kinks is not completely cancelled. The interaction of hydrogen-dislocation can be fully described in terms of kinks in dislocations.

Research highlights
► Original ultrasonic data on hydrogenated copper aged ≥64 days are presented.
► The interpretation was realized in terms of kinks in dislocations.
► A hydrogen viscosity is assumed added to phonon viscosity.
► An evidence of high hydrogen mobility along dislocation core is found.
► A depinning process is observed if the sample temperature exceeds 100 °C.