Logarithmic Creep of Copper and Aluminium

Abstract

Transient creep of polycrystalline OFHC copper and aluminium of 99·95 % purity was studied by the method of incremental loading, in tension at room temperature. All specimens were initially annealed, but some were also prestrained 10% either in tension or in compression before creep. The creep strain ε was expressed by ε = S log (1 + t/t _o), and the dependence of the parameters s and t_o on the level of the applied tensile stress and on the sign of the prestrain was examined. The structure sensitivity of both parameters, indicated by the results, was discussed in terms of a simple stochastic model; the latter is based on the concepts of a spectrum of energy barriers to dislocation motion and the tendencyof dislocation assemblies to assume minimum-energy configurations.The observations point to the potential usefulness of such relatively simple investigations in assessing the creep resistance and studying structural detail of metals and alloys.