Influence of hydrogen on the deformation-induced martensitic transformation and crack development in metastable austenitic steels. An approach combining experiment and atomistic simulations

• Applicants: Dr. Brian Kagay; Dr. Matous Mrovec; Professor Dr.-Ing. Stefan Weihe
• Subject Area: Computer-Aided Design of Materials and Simulation of Materials Behaviour from Atomic to Microscopic Scale ; Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 535647705

The aim of this project is to investigate the influence of hydrogen on the deformation induced transformation of fcc austenite into bcc ’-martensite and the initiation and growth of fatigue cracks in a metastable austenitic steel X6CrNiNb18-10. Despite a broad application of austenitic steels, the impact of hydrogen on the martensitic transformation as well as on the strength and ductility of these alloys is still not fully understood. In fact, there is a controversy about whether hydrogen enhances or impedes the phase transformation and which are the governing micromechanisms of H assisted fracture. To project relies on a combination of distinct experimental techniques and dedicated atomistic simulations. The experimental work includes mechanical tests under various conditions and detailed microscopic characterization from meso to nano scales. The atomistic simulations encompass both ab initio electronic structure methods and novel interatomic potentials based on machine learning. The added value of the proposed work is the close collaboration and exchange of data between experiments and simulations. Even though the effect of H originates at the atomic scale (e.g., H trapping and diffusion), it manifests itself on all micro, meso and macro scales (e.g., stacking fault energies, slip planarity, dislocation microstructures). Hence, understanding of the atomic scale mechanisms is fundamental for a proper interpretation of all experimental observations. Apart from the scientific objectives of this project, there are also important practical aspects related to the safety of hydrogen tanks and other components in the emerging „Hydrogen Economy“. This can be achieved only via thorough knowledge of the underlying mechanisms that are responsible for the hydrogen embrittlement in this important class of materials.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Ralf Drautz