30 hp - Microstructure Relationships in Developed Low-Alloy Steels Introduction Thesis work is an excellent way to get closer to Traton and build relationships for the future. Many of today's employees began their Traton career with their degree project. Background The development of advanced steels for automotive applications requires careful control of microstructure throughout manufacturing and heat-treatment processes. In particular, controlling austenite grain growth during high-temperature heat treatment is important for achieving the desired final material properties. Austenite grain growth is strongly influenced by the presence, size, distribution, and stability of precipitates. Fine precipitates such as AlN, NbC,N, and VC,N can inhibit grain-boundary movement through the Zener pinning effect. However, the precipitate state is itself affected by the steel composition, heat-treatment conditions, and previous thermomechanical processing history. Understanding these relationships is therefore important for controlling grain growth in newly developed low-alloy steels. Objective The main objective is to determine how steel composition and processing history influence precipitate characteristics and, consequently, the resistance of austenite grains to growth during the final high-temperature heat treatment. Particular attention will be given to identifying which combinations of steel composition and processing history provide the greatest resistance to grain growth and to understanding the underlying mechanisms responsible for the observed differences. Job description This master's thesis investigates the relationship between processing history, precipitate evolution, and austenite grain growth in five model alloys designed to investigate low-alloy steels for automotive applications. Each steel has been processed using two different rolling routes, resulting in ten different initial material conditions. These materials will subsequently undergo controlled thermal cycles with different cooling rates using dilatometry. The aim is to generate different precipitate states and initial austenite grain structures before subjecting the materials to final heat treatments in the temperature range of 1000–1100 °C, followed by rapid cooling. The microstructure will be characterized using scanning electron microscopy SEM and energy-dispersive X-ray spectroscopy EDS, supported by thermodynamic calculations using the Thermo-Calc Software package. Electron backscatter diffraction EBSD will be used to investigate austenite grain size and grain-size distributions, as well as relevant grain-boundary characteristics, crystallographic texture, kernel average misorientation KAM, and phase information. If required and feasible within the project timeframe, extraction replicas will be used to characterize precipitates that are too small to be reliably resolved using SEM. Education/program/focus Indicate education, program, or focus: Master’s student in Mat
