Rapid Stress Relief of Ti-6Al-4V Titanium Alloy by Electropulsing Treatment

This study investigates the effectiveness and underlying mechanisms of electropulsing treatment (EPT) for rapid stress relief of Ti-6Al-4V titanium alloy. Stress relief is an essential step in manufacturing processes to ensure long component lifespan. Residual stress accumulation within a component is often undesirable, as it may lead to premature failures. Currently, the stress relief of titanium alloys is typically carried out using an annealing heat-treatment process in a vacuum furnace. However, this method is time-consuming, usually requiring several hours. In this paper, an alternative fast stress relief method by EPT was investigated. A controllable pulsing treatment using alternating high density pulsing current with short pulse width was carried out. Results showed that EPT is effective in relieving residual stress in Ti-6Al-4V alloy. Up to 90% of the surface residual stresses induced by shot peening were successfully relieved by EPT with a treatment duration of only 114 ms. Reductions of low-angle grain boundaries (2-10°), local misorientation, and deformed grains were observed, while no significant grain growth or phase transformation was found. The stress-relief mechanism of EPT is attributed to the combined effects of dislocation movement driven by electron wind force (EWF), dislocation creep at elevated temperatures, and dislocation glide due to local yielding of residual stress under high-temperature conditions. The temperature rise during EPT was identified as a significant factor enabling stress relaxation.