Ultrasonic evidence of the existence of two hydrogen Snoek–Köster relaxations in high-purity single crystal copper

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

“…For comparison, the inset shows the ultrasonic attenuation for a high purity copper measured in an hydrogen free [2] and 3 days aged [6] hydrogenated samples, where the respective dislocation background were subtracted from the experimental data.…”

“…This effect can explain the behaviour observed in both attenuation and elastic modulus at temperatures between 50 K and 140 K. This work brings strong experimental evidence of the validity of the kink picture for dislocation vibration and shows that the geometrical kinks can play the role of impurities in relation to the interaction with the hydrogen diffused in the crystal. Inset: ultrasonic attenuation for a high purity copper measured in a hydrogen free [2] and a 3 days aged [6] hydrogenated samples, where the respective backgrounds were subtracted from the experimental data. Figure 1, obtained using equations (1) and (2).…”

“…The resonance background was subtracted from original data in both curves, in order to show more clearly the relaxation components. In the uncharged sample the NWR and BR can be clearly identified, while in the hydrogen charged and aged sample the presence of two HSKR is noticeable [6]. The absence of NWR and BR observed in Figure 1 could indicate that the hydrogen is still near the dislocation lines, inhibiting these peaks; while the absence of the two HSKR also indicates that the hydrogen atoms could not be in the dislocations surroundings.…”

“…The specimen, previously oriented by the Laue X-ray method, was 5.7 % deformed by compression in the direction <111>. After that it was charged with hydrogen during 72 hours at 0.2 MPa and 573 K. Further details of the experimental setup were described elsewhere [6]. For this work, ageing and ultrasonic measurements on the sample were accomplished in three stages.…”

“…In this paper we present measurements of phase velocity and attenuation of ultrasonic RF pulses, in a hydrogenated crystalline copper sample aged between 64 and 97 days, in order to study the interaction of diffused hydrogen with kinks in dislocations, and their comparison with those made at early stages of aging and published elsewhere [6].…”