Bainitic and Martensitic Microstructures Revealed by EBSD

To understand and to tailor the properties of nuclear materials, it is essential to investigate their microstructure. EBSD systems in SEMs facilitate local crystal orientation measurements providing surface mappings in which each point is characterized by three Euler angles [1]. This data is used to reveal microstructural features such as grains, their size and -shape, grain boundaries and other details.
In the present work, a dedicated EBSD evaluation software was developed and applied to study the type of grain boundaries. Former austenite grain boundaries are revealed and within certain limitations, it is possible to differentiate between packets and blocks. Additionally, details about the variant selection during the martensitic transformation are provided and differences between bainitic steels and ferritic/martensitic steels are identified. This information may be of use to understand grain boundary related differences regarding cluster formation and sink strength.