Room-temperature stress reduction in welded joints through electropulsing

• Residual stress in welds are typically reduced by heat treatment or peening. • A room-temperature process using sharp electrical pulses was demonstrated. • The electrical resistance, which reflects defect density, decreased by 30 %. • The microhardness and X-ray diffraction residual stress decreased by 40 %. • The low-angle grain boundary and misorientation angle significantly decreased. Conventional residual stress mitigation techniques involve long processing times at high temperatures and/or mechanical loading to build plastic compressive stress below the surface. In this study, we present a new residual stress mitigation methodology at near ambient temperature in less than a minute. This is demonstrated on a welded joint of 316 L stainless steel, where low-frequency DC current pulses are shown to recrystallize the specimen and reduce residual stress. We present experimental evidence of ∼30 % reduction in electrical resistance, which corresponded to ∼40 % decrease in both microhardness and residual stress, measured by the X-ray diffraction tests. Similar improvement was qualitatively observed through significant decrease in the low-angle grain boundary density, which also reflects the decrease of the residual stress. The technique can be applied to relieve residual stress in conditions difficult for the conventional processing, such as locations with extreme space constraints or objects that cannot be heat treated.