Precipitation strengthening is an important parameter controlling the mechanical properties of low carbon steels. These precipitates can be very fine, below 100 nm in size. Thus, proper characterization of such fine microstructural features requires high resolution imaging techniques. Normally, this would involve characterization using a transmission electron microscopy (TEM). In this work, field emission scanning electron microscope (FE-SEM) was applied successfully in the characterization of Nb (C, N) precipitates using carbon extraction replicas and thin foils. FE-SEM observation of low carbon steel replicas and thin foil shows the presence of Nb (C, N) precipitates in ferrite. The FE-SEM could analyze small particles (below 50 nm) but the analysis in 'bulk' specimens must be carried out at low voltages to preserve volume resolution, resulting in very weak signals. However, the foils and the carbon extraction replicas could be analyzed in the FE-SEM using relatively high voltages since the interaction volume effect is no longer a problem.
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