Mechanical Behavior and Microstructural Changes Associated with Tensile Deformation above the Martensite Start Temperature during Quenching and Subsequent Partitioning of a Low‐Alloy 37SiB6 Steel

Advanced pressing processes combine the short cycle times of conventional press hardening with the advantages of experimental quenching and partitioning steels. Their design typically involves complex thermal and mechanical load paths. In this study, a custom‐designed experimental heating/cooling setup is used to characterize a low‐alloy 37SiB6 steel under conditions close to an envisioned press‐partitioning process: After austenitizing, specimens are deformed to different target strains during rapid quenching above the martensite finish temperature, followed by partitioning at constant temperature. It is demonstrated that using specialized heat‐resistant coatings allows to simultaneously perform digital image correlation and infrared thermography to determine strain and temperature fields, and the thermomechanical behavior is discussed during the entire experiment as a function of applied strain, temperature evolution, and strain rate. Microstructural analyses reveal that these thermomechanical load cases lead to the formation of predominantly martensitic microstructures with small regions of retained austenite. The results indicate that the morphology and distribution of martensitic microstructures and the amount of retained austenite can be significantly affected by the amount of plastic deformation introduced during quenching and the partitioning temperature. This clearly shows that careful thermomechanical experimentation can be beneficial for the design and further improvement of complex quench and partitioning treatments.