Analysis of the Complex Inclusions in Rare Earth Element Treated Steel

19^th May 2023 | Author: Hui Jiang

Research reveals that the rare earth (RE) elements (such as La and Ce) can improve mechanical properties of steels by modifying inclusions in the steels. Therefore, the research on inclusions in rare earth steel is conducive to improving the process and performance of rare earth steel. Measurement of the properties (size distribution, amount and chemical composition) of inclusions related to the RE elements are of great importance.

Challenge

However, the RE elements are heavier than Fe-matrix, and often coincide with the non-metallic inclusions containing light elements, i.e. Al, Mn, Mg, Si and S, to form complex inclusions. In these cases, it is desirable to treat the inclusion as a single feature, even though it is made up of multiple parts.

It is difficult to automatically analyse these complex inclusions, because these complex inclusions have multiple parts with very different contrast in the back scattered electron (BSE) image and cannot be detected as a whole automatically using the conventional approach of thresholding on desired phases. This results in errors in both morphology and chemical composition measurements, and thus could mislead the evaluation on the effect of RE elements additions. An example of a BSE image of a complex inclusion is shown in Figure 1.

Figure 1: BSE image of a complex inclusion.

Solution

In the latest AZtecSteel, the automated inclusion analysis platform, it is possible to detect an inclusion that contains multiple phases, some of which are lighter than the matrix and some of which are darker, as a single inclusion. In order to do this, we have implemented a functionality that allows the part of the grey level range that should not be thresholded to be selected – so that the rest is thresholded (Figure 2a). Morphology and composition can, therefore, be correctly measured as a whole (Figure 2b & 2c).

a.

b.

c.

Figure 2 a.: Complex inclusion is detected as whole; b.: Morphology and composition of the complex inclusion are measured correctly as a single inclusion; c.: EDS sum spectrum from the complex inclusion.

Hopefully, this gives you an insight of how to automatically detect and measure complex inclusions in RE element treated steel for statistical analysis using AZtecSteel.

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