Ultrasonic investigation of the interaction hydrogen-dislocations in copper crystals

TL;DR

This study investigates how hydrogen interacts with dislocations in copper crystals using ultrasonic methods, revealing hydrogen segregation at dislocation cores and its effects on dislocation mobility and resonance at various aging stages.

Contribution

It provides experimental ultrasonic data showing hydrogen's segregation at dislocation cores and its influence on dislocation dynamics in copper, a novel insight into hydrogen-dislocation interactions.

Findings

Hydrogen segregates mainly at dislocation cores, inhibiting certain relaxations.

Mobile hydrogen contributes to viscosity via kink-chain resonance.

Hydrogen freezing immobilizes dislocations, affecting their resonance behavior.

Abstract

In this paper we present experimental data of ultrasonic velocity and attenuation obtained in a high purity crystalline sample of cooper hydrogenated by gaseous charge. The sample is oriented in the <111> 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-K\"oster relaxations verified at earlier aging stages. Despite of this, a contribution to viscosity in the kink-chain resonance is provided by the mobile hydrogen in the dislocations 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 hydrogen-dislocation can be fully described in terms of kinks in dislocations.