Misorientation and dislocation evolution in rapid residual stress relaxation by electropulsing.

• Role of electric current pulsing on residual stress induced by shot peening is studied. • High-current density electropulsing effectively reduces in-plane compressive stresses. • Subsurface microstructure after electropulsing is characterised by low defect density. • Annihilation and relaxation of dislocation substructure are attributed to the electron wind force and the local transient temperature spikes from high current density pulsing. This study investigates the effect of high current density electropulsing on the material in a rapid stress relaxation process. An AISI 1020 steel was shot-peened to induce surface compressive residual stresses in a controlled manner and subsequently electropulsed to investigate the changes in microstructure and defect configuration. AISI 1020 steel was chosen as it has a simple microstructure (plain ferritic) and composition with low alloying conditions. It is an appropriate material to study the effect of transmitting electric pulses on the microstructural defect evolution. A combination of electron-backscattered diffraction and transmission electron microscopy proved to be an effective tool in characterizing the post-electropulsing effects critically. By application of electropulsing, a reduction in the surface residual stress layer was noticed. Also, reductions in misorientation and dislocation density together with the disentanglement of dislocations within the cold-worked layer were observed after electropulsing. Additionally, the annihilation of shot-peening-induced deformation bands beyond the residual layer depth was observed. These effects have been rationalised by taking into account the various possibilities of athermal effects of electropulsing. [Display omitted] [ABSTRACT FROM AUTHOR]