Analysis of creep in long range ordered CuZn in terms of thermally activated overcoming of barriers

Brass of nominal composition Cu–48 wt.% Zn was creep tested at temperatures from 573 K to 723 K. In this temperature interval the long-range ordered β′ phase exists. In addition to conventional creep experiments, constant-structure creep was studied by means of sudden applied-stress changes in the steady-state creep region. A proper combination of the experimental results makes it possible to analyze the deformation process as a thermally-activated overcoming of simple box-shaped obstacles. The Helmholtz and Gibbs free energies of activation and characteristic obstacle spacings can be estimated in this way. Possible refinements of the model, which include a more realistic obstacle shape and a dependence on effective stress are discussed.