An experimental study on stress relaxation behaviour of high strength steel wire: Microstructural evolution and degradation of mechanical properties

In this study, a series of experiments including stress relaxation, nanoindentation, tension loading experiments, and transmission electron microscope (TEM) examination were performed to investigate microstructural evolution, the stress relaxation behavior, and the influences of stress relaxation on mechanical properties of high strength steel wire. The stress relaxation experiments were performed on a single steel wire for 1000 hat three initial stress levels to characterize the stress relaxation behavior of the tested material. Microstructural evolution of the specimens deformed by stress relaxation was observed and analyzed using TEM examination. Long-term relaxation behavior was then calculated and investigated. Finally, the influences of stress relaxation on material properties were studied by performing nanoindentation and tension loading experiments on the deformed relaxation specimens. The degradation of mechanical properties under stress relaxation was interpreted through a micromechanism regarding the microstructural evolution and the grain boundary strengthening. The results from the present study can be used for practical designs as well as for assessing the stress relaxation behavior of high strength steel wire. (C) 2020 Elsevier Ltd. All rights reserved.