Internal Friction of Copper and Copper Alloys

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Abstract
A systematic experimental study has been made of the effect of adding small amounts of gold to copper on the dislocation damping in copper measured at 37 kc in longitudinal resonance. The results have been classified in terms of the dependence of the damping on strain amplitude and time with temperature and composition as parameters. The data on amplitude dependence confirm the theoretical results of Granato and Lücke over the range 10−4 to 10−3 atom % gold, where the decrement, Δ, is given as a function of the strain amplitude of oscillation, ε, by Δ=Δ0+(B′/ε½) exp (−A′/ε). The dependence of A′ and B′ on concentration and other parameters is discussed. Above 150°C, at strains large enough for the damping to vary with strain amplitude, the damping may depend on time, t, at constant amplitude in a reversible manner. This dependence may be represented by α exp(−βt⅔)+ct+d with the exponential dominating in the pure specimens and the linear term at 10−3 atom % gold. A detailed consideration of this behavior points strongly towards a vacancy-dislocation interaction as the source. About 280°C, and independently of gold concentration, the damping starts to rise steeply with at least one thermally activated process involved. It appears that vacancies are involved here too. In supplementary measurements, the increase of resistivity of copper due to gold impurities was determined as 0.472 μohm cm per atom % gold.