Ultimate lateral resolution reveals complexity of microstructure

Metallic coating developments concentrate on altering the microstructure. However, characterising this often complex microstructures is not easy.

Thanks to the FEG-EPMA with SXES (soft X-ray emission spectrometer) detector, OCAS has been able to study microstructures using much higher resolution.

E.g. Below a mapping across a zinc-aluminium-magnesium coating is shown using the old W-EPMA and newer FEG-EPMA

W-EPMA

W-EPMA mapping of zinc-aluminium-magnesium coating

 

FEG_EPMA ocas equipment ZAM

FEG-EPMA mapping of zinc-aluminium-magnesium coating

Using FEG-EPMA the spatial resolution of 100 nm can be reached. At this resolution, the microstructure can clearly be seen and more importantly the phases can be identified. Understanding the microstructure and identifying the present phases (also on a small scale) enables us to interpret and understand corrosion data more elaborately. This is of course indispensable for metallic coating development projects.

The example below shows a linescan across a needle of approximately 300 nm wide yielding the expected Fe4N stoichiometry by quantification. The detection limit for these nitrogen analyses is around 500 ppm with the optimized crystal for nitrogen. The smallest needle clearly detected was 100nm in width.

FEG-EPMA OCAS equipmentFeN needles

“Our FEG-EPMA with SXES detector allows us to better understand the link between microstructure and composition. It is great to see striking maps appear so quickly.”

Cynthia Roegiers, lab technician structural material characterisation and main operator FEG-EPMA, OCAS