Study of local mechanical properties and deformation mechanisms of the soft zone of welded joints of high-strength steels

High-strength steels (HSS) are crucial in the production of lightweight structures. Their welding creates a distinct heterogeneous heat-affected zone (HAZ) in which a softened zone with locally lower mechanical properties forms. This critical zone acts as a weak point, concentrates strain, and can initiate failure, thereby compromising the structural integrity of the welded joint. Detailed understanding of the local behaviour of this zone is insufficiently investigated. Standard tests provide only basic data, which limits the reliability of simulations and the integrity assessment of steel structures. The article deals with the characterization of the local mechanical properties and deformation behaviour of the HAZ softened zone using the DIC (Digital Image Correlation) and nanoindentation techniques. The combined approach enables a comprehensive understanding of the mechanical properties of the HAZ subzones, crucial for assessing the reliability and integrity of welded structures.