Amplitude-dependent internal friction in dilute copper—aluminium alloys with three kinds of peaks

Abstract

Amplitude-dependent internal friction is measured on 99.999% Cu and dilute Cu—Al alloys, annealed and lightly prestrained. The measurements are made with an inverted torsion pendulum, at temperatures between 300 K and 90 K, and at about 1.6 Hz. Three kinds of peaks are observed: (1) the peak in the amplitude dependence, which is shifted to higher amplitude, and the peak height increases, either with increasing concentration or with decreasing temperature; (2) the peak in the concentration dependence, which exhibits the ‘peaking effect’; the peak is shifted to higher concentration, and the peak height increases, as the amplitude increases; (3) the peak in the temperature dependence, which is shifted to lower temperature, and the peak height increases as the amplitude increases. These results are interpreted in terms of frictional forces and the associated relaxation of dislocations oscillating in random solid solution.