Microstructural characterization and quantification of Zn–Al–Mg surface coatings

The microstructure of Zn–Al–Mg coatings on steel sheets is characterized with the energy dispersive X-ray technique. Optimum parameters on the scanning electron microscope with a field emission gun have been found in order to laterally resolve the fine structure of the individual phases. A quantification of the microstructure is done with a mean shift algorithm that is usually applied for image segmentation in pattern analysis. This nonparametric technique is here based on the chemical composition and the spatial domain. The measured area is partitioned by a quantitative feature space analysis into phases with similar chemistry. A backscattered electron image is compared with the results of the X-ray point map of the same area. As an application the influence of the chemical composition of the melt on the resulting microstructure is compared for two different alloys.