Two- and three-dimensional microstructural characterization of a super-austenitic stainless steel

The microstructure of AL-6XN, a commercial super-austenitic stainless steel, was investigated using novel two- and three-dimensional (3D) analysis and characterization techniques. The austenite matrix, the second-phase σ precipitates, and the relationships between them have been analyzed, with particular emphasis on the true 3D microstructure of the material, including grain boundary character, grain morphologies and connectivity. A combination of serial sectioning with electron backscatter diffraction (EBSD) analysis allowed for reconstruction of individual grains, and definition of all five degrees of freedom of the grain boundary planes. Second-phase σ particle size and morphology, crystallography, composition, potential formation mechanisms, orientation relationships, and coherency with the matrix have been analyzed. These results provide boundary conditions for atomistic calculations of specific grain boundary structures as well as the basis for mesoscale image-based models of mechanical behavior of the microstructures.