Stress relaxation of a eutectic alloy in the superplastic condition

Abstract

Stress relaxation experiments on fine-grained samples of the SnPb eutectic alloy exhibit precipitous decreases in strain rate at nearly constant stress. However, comparison with creep results on the same material demonstrates that this behavior does not reflect any threshold stress for creep deformation. The relaxation behavior is well described by a mechanical analog model which incorporates an anelastic element similar to reported “superanelasticity” in this alloy. Creep of this material at a low stress can be described by a power law, with the strain rate proportional to the third power of stress, or by the influence of a threshold stress about an order of magnitude smaller than the false threshold of the stress relaxation experiments.