Advanced Chemometric analysis of photoemission Electron microscopy imaging for detecting non-metallic inclusions in steel materials

The accurate identification of non-metallic inclusions (NMIs) within steel matrices is critical for high-quality steel production. This study employs synchrotron radiation-based X-ray absorption photoemission electron microscopy (X-PEEM) to investigate NMIs in ultra-high-strength steels. Ca-L2,3-edge X-ray absorption spectra were acquired for six NMIs at both room temperature and 400 °C, allowing a comprehensive exploration of structural changes, chemical compositions, and phases. Complex X-PEEM images were analyzed using advanced chemometric techniques, including Principal Component Analysis (PCA), K-means clustering, Fuzzy-means clustering (FMC), and Multivariate Curve Resolution–Alternating Least Squares (MCR-ALS). These methods allowed for the segmentation of X-PEEM images into distinct compositional zones. K-means clustering effectively identified regions of interest (ROIs) within NMIs, while PCA facilitated the microstructure variances of NMIs. Additionally, K-means and FMC revealed detailed compositional variations at the nanoscale. MCR-ALS proved particularly useful in uncovering changes in NMIs after annealing. This study pioneers the integration of X-PEEM with advanced chemometric methodologies, providing qualitative and quantitative spectromicroscopic insights. It significantly enhances our understanding of NMIs formation and alteration processes in ultra-high-strength steels, contributing to the advancement of materials science and steel production optimization. Furthermore, the methodologies and findings presented here serve as a guide for analyzing similar data sets of steel samples, offering valuable insights for future research and industrial applications in steel engineering.