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Abstract
The effect of alloying on creep and grain-boundary sliding behaviour has been investigated in a series of four copper–aluminium solid solutions containing 5, 9, 14, and 18 at.- %Al. All tests were carried out at 400° C and at stresses between 40 and 150 N/mm2. The ratio (γ) of the strain contributed by sliding (εgb) to the total strain (εT) was between 0·06 and 0·22 for all the specimens, showed no strong dependence on either creep stress or strain and, to within the accuracy of the results, did not depend on alloy content (i.e. on stacking fault energy).
The stress exponent and the activation energy for overall creep both varied systematically with aluminium content; the former increasing and the latter decreasing with increasing aluminium content. The minimum creep rate was proportional to the square of the stacking-fault energy. The creep ductility decreased (by a factor ∼10) with decreasing aluminium content and this was attributed to an increase in diffusivity.