A possible stabilizing effect of work hardening on the tensile performance of superplastic materials

Abstract In general, the process of superplastic deformation is regarded as steady-state so that the flow stress is given as a function of the strain rate only, thereby emphasizing the significance of the strain rate sensitivity and its determining methods. In this work, in addition to the important role of the strain rate sensitivity, it is shown that it is necessary also to consider the stability criteria for real, stable superplastic deformation through other factors such as work hardening. A possible scenario is proposed to describe the process whereby the work hardening rate may stabilize the deformation process when a perturbation occurs in the cross-section of the sample. The assumption of a work hardening effect is confirmed by its application for interpretation of the systematic deviations observed between the strain rate sensitivities determined experimentally using different experimental methods.