Comparison of thermally activated overcoming of barriers in creep of aluminum and its solid solutions

The creep behavior of two aluminum solid solutions (Al-5.5 wt.% Mg and Al-13.7 wt.% Zn) was tested at temperatures from 573 to 773 K. Besides conventional creep experiments, constant structure creep was also studied by means of sudden change of the applied stress in the steady-state creep region. According to Nakayama and Gibeling, results of both types of experiments can be rationalized on the basis of the kinetics of dislocation glide controlled by overcoming of obstacles. Nakayama and Gibeling have also suggested a procedure that makes it possible to determine the basic characteristics of the process, i.e., the Helmholtz free energy, the Gibbs free energy and the obstacle strength, by means of stress-change experiments at different temperatures. The results of the procedure applied to the solid solutions under consideration can be compared with results of a similar study of creep of pure aluminum published previously by the present authors.