SEM EDS Analysis of Low Carbon Steel Composition

Low-carbon steel produced throughout the world is used in automobiles, construction, oil and gas pipelines, and many other applications. Many of these utilize aluminum to create a fine-grained microstructure due to the precipitation of nanoscale aluminum nitride that pins grain boundaries.

One of the downsides to aluminum deoxidation is that it leaves a population of micron-sized oxides, which are prone to agglomeration and become crack initiators during bending, welding, or fatigue testing.

SEM distinguishes particles from the matrix by setting a threshold on the backscattered electron image. Most steel inclusions have a lower average atomic weight than the iron matrix, showing up as dark particles in a brighter background.

Energy dispersive X-ray spectroscopy (EDS) collects chemical information on each inclusion, which can then be plotted on a ternary diagram. The color represents the size, and the location represents the normalized composition for the elements represented on the corners.