Influence of laser-induced microstructure notches on the configuration of residual stresses in a steel plate

Among technological problems related to manufacturing materials with controlled and localized properties, the effect of a microstructure notch is still unsatisfactorily recognized. Laser modification of selected areas of material structures is one of the most promising technologies in the field. The work presents selected variants of generating the intended microstructure changes in the near-surface areas of steel plates by means of a laser beam. A field of residual stress was generated in the examined steel as a result of phase transformations accompanying the laser treatment. Both the microstructure changes and configuration of residual stresses were identified by means of the optical microscopy, and X-ray diffraction technique. The results, additionally related to crystallographic texture, allowed to characterize the microstructure modifications and to interpret a potential change of mechanical properties. It was found, that the level of the stresses and its range can vary essentially with parameters of the laser treatment, which gives one a chance to control the behaviour of a material in the conditions of mechanical loading, by exploitation of a structure element.