High temperature creep in a Cu-11 at. % Al solid solution

Abstract

The creep in a Cu-11 at. % solid solution was investigated by the isothermal tests technique. In the region of lower temperatures and lower creep rates, respectively, the apparent activation energy of creep is stress independent and its value is close to that expected for the activation enthalpy of self-diffusion of aluminium in the solid solution. The stress exponent n = η In δ_έ/δ In a increases with stress from 4 to 5·5. Viscous motion of dislocations connected with the interaction of aluminium atoms with dislocations was suggested to be the rate-controlling mechanism. In the region of higher temperatures and higher creep rates, respectively, two mechanisms seem to operate. The apparent activation energies are strongly stress dependent and are considerably higher than the activation enthalpy of self-diffusion of copper in the solid solution. The stress exponents n generally depend on stress and temperature. The results for the higher stress interval 6·0–11·0 Kg mm⁻² can be correlated with the model of non-conservative motion of jogs on screw dislocations if every non-conservative jump of a jog by one interatomic distance is connected with cooperative absorption or emission of an effective number of about 1·3 vacancies. The results for the lower stress interval l·0-5·0 Kg mm⁻² have not been correlated with any of the known dislocation mechanisms.