INTERNAL-STRESSES, STRESS CHANGE TESTS AND THE FORMULATION OF THE RECOVERY CREEP EQUATION

The internal stress for recovery creep, a„ can be deduced from stress change experiments and it is traditional to assume that the steady-state creep rate is proportional to (a—a¡)", where a is the applied stress and n is a constant. It is shown that the behaviour observed during stress-dip experiments on alloys in which creep is controlled by the influence of solute drag on dislocations, cannot be rationalized by this formulation. It is necessary to use an alternative relationship such that sccff"-1 (cr — erg), where n = 3. This equation is more compatible with the expected dependence of the creep rate on the product of the dislocation density and velocity. A rationale for the new formulation is presented and consideration is also given to materials which are not controlled by solute drag effects. © 1991 Taylor & Francis Group, LLC.