A micro-mechanism model of residual stress reduction by low frequency alternating magnetic field treatment

Low frequency alternating magnetic field treatment is a non-thermal method used to process welded samples with internal residual stress. The purpose of the paper is to investigate the quantitative correlation between magnetic treating parameters, magnitude of stress relaxation and the stress relaxation mechanism. The microstructure change of the material during magnetic treatment is also observed by TEM and discussed from the point of view of dislocation behavior in the processed material. The experimental results indicate that low frequency alternating magnetic field treatment is an effective method in reducing residual stress in steels. The main reason for the stress reduction is the even-distribution of dislocation due to magnetic treatment. A physical model of residual stress relaxation by magnetic treatment is raised based on the experimental results and microstructural observation that well explain the micro-mechanism of this method.