Effect of Cu concentration on the high-temperature creep behavior of AlCu solid solution alloys

The creep behavior of AlCu alloys containing 2 and 4 wt.% Cu was investigated at a temperature of 813 K and over a stress range of 0.5–10 MPa. The present results, along with previous data on AlCu alloy, suggest the presence of three regions of deformations: region I at low stresses, region II at intermediate stresses and region III at high stresses. In region I, the creep curves showed the characteristics of dynamic recrystallization and the stress dependence of minimum creep rate n is approx. 6.5. The concentration dependence of creep rate in this region is a reflection of a decrease in stacking fault energy with solute concentration. In region II, the creep characteristics including the stress exponent, n (∼ 3) and the shape of the creep curve (sigmodial primary creep) are consistent with viscous glide control. The transition stress between regions I and II is inversely proportional the square root of Cu concentration, in agreement with the prediction of the climb-viscous glide criterion for solid solutions. In region III the creep characteristics are not entirely consistent with any of the existing deformation mechanisms. The transition from region II to region III is due to the dislocations breakaway from their solute atmospheres.