Thermal activation of steady-state creep in polycrystalline copper

High purity (99.9%) polycrystalline copper wires have been creep tested at atmospheric pressure and at intermediate temperatures of 573K, 673K and 773K (T/Tm = 0.42-0.57), under uniaxial tensile stresses of 7.08, 14.16 and 21.24 MPa in order to determine the activation parameters of steady-state creep. The tension creep tests were conducted using a stress incremental technique (σ1 < σ2 <σ3). The stress exponent of the steady state creep rate n is close to 2 and the activation energy Q1c is about 60 kJ/mol. Activation analyses of the data have been made to identify the deformation mechanism(s) and to link the external parameters with the model parameters through the operational parameters n and Q1c. The creep deformation is attributed to a boundary mechanism involving grain boundary sliding and Coble diffusion. A model is proposed for the boundary mechanism. (author). 13 refs, 9 figs