Characterization and Determination residual stresses and strength properties in cold formed welded TWIP- and TRIP steels

Modern deep-drawing steels exhibit a high work hardening potential based on various deformation-induced changes in the microstructure, such as the martensitic transformation of initial retained austenite or plastic deformation-induced twinning. The stability of the achieved work hardening state, in conjunction with the temperature cycles to which components are subjected during welding, is of fundamental importance for the resulting component strength. Synchrotron and X-ray diffraction texture analyses, macro- and micro residual stress determinations, and retained austenite analyses of welded TRIP and TWIP steel are used to characterize the relationships between the temperature field and the development of the residual stress and work hardening state. In-situ synchrotron experiments and methods of X-ray interference line analysis combined with mechanical microindentation tests are employed to investigate the retained austenite content and the work hardening state, as well as its changes due to thermal cycles and mechanical stresses, allowing for highly differentiated assessments.