Welded joint structure and phase composition modified by plastic deformation

The paper presents the structural analysis of the welded joint phase state subjected to plastic deformation. The analysis is carried out using the transmission electron microscopy. The type St3 steel is used for the welding material. The effect of plastic deformation is determined for the material morphology, phase composition, defect structure, and its parameters. Investigations are conducted at 1 mm distance between weld and base metals at the deformation degree ranging between 0-5%. Plastic deformation does not lead to a structural quality modification (hypopearlitic steel structure is present as before), while the qualitative parameters are changed such that a portion of the perlite component becomes more defective and first transforms to fractured perlite and then ferrite, and the perlite volume fraction then decreases. Polarization of the dislocation structure is observed, however, does not induce internal stresses capable to disintegrate the specimen.