Lubrication agents of dislocation motion at very low temperature in cold-worked aluminium

Measurements of the dynamic modulus and internal friction of ultrahigh purity aluminium were performed after low-temperature plastic deformation. The salient result is that the low-temperature deformation provokes an important decrease of the elastic modulus and a simultaneous disappearance of the Bordoni relaxation. These results confirm the existence of a lubrication process proposed recently to explain the very small value of the critical resolved shear stress observed at low temperature in FCC metals. Further insight into the nature of the defect species responsible for this lubrication has been attained by comparing the results obtained after low-temperature irradiation and those following low-temperature plastic deformation and subsequent anneal sequences at different temperatures. Vacancies are believed to be the defect species responsible for the lubrication.