Relaxation of residual stress in aluminum alloy rings by pulsed high magnetic field: Relieving mechanisms and performance evaluation

Residual stress is commonly present in metal components, potentially leading to structural instability and reduced strength. Thus, effective elimination of residual stress is essential in manufacturing large metal components. Traditional methods for stress relief include energy-based and mechanical approaches. However, energy-based methods are time-consuming and can weaken component strength, while mechanical methods may damage contact surfaces and cause localized stress concentrations. This paper introduces a novel technique for relaxing residual stress using pulsed high magnetic fields. The method applies a pulsed magnetic field to the ring’s inner surface, inducing a strong, non-contact Lorentz force that triggers slight plastic deformation, releasing residual stress in the elastic regions. Remarkably, the process takes only a few milliseconds. The study examines the mechanisms behind residual stress relief via pulsed magnetic fields and designs a device for stress elimination in large aluminum rings. Initial validation through bulging experiments on 6061 aluminum alloy rings (118 mm diameter) showed that the electromagnetic bulging process improves micro-deformation uniformity, promotes dislocation motion, generates sub-grain structures, and refines grains, thereby relieving stress. A large-scale electromagnetic bulging platform was then designed for 5A06 aluminum alloy rings (717 mm diameter). In-situ experiments demonstrated that a plastic deformation of 1 % eliminated up to 84.9 % of residual stress, indicating substantial stress relief. Finally, the study compared the effectiveness of stress elimination across different surfaces under various discharge bulging modes and analyzed the reasons for these differences. This method significantly enhances the efficiency and effectiveness of residual stress elimination in large aluminum alloy rings.