Nanoscale investigation of residual element segregation in steels produced through low CO2 routes

Press-hardened steels (PHS) produced through low-CO2 metallurgical routes can contain higher levels of residual elements originating from scrap-based processing. These residuals (e.g., Cu, Ni, Sn, P) may segregate to structural defects during steel processing and subsequent thermomechanical treatments, potentially affecting phase transformations, hardenability, and local mechanical response [1].

In this work, we investigate the segregation behavior of residual elements in Electric Arc Furnace (EAF)-based PHS grades using Atom Probe Tomography (APT). APT specimens were prepared by focused ion beam (FIB) to probe both prior-austenite grain boundaries and martensitic lath boundaries, where segregation is expected. APT analyses reveal nanoscale enrichment of residual elements at specific crystallographic interfaces.

Quantitative composition profiles show that elements such as P, B, Ti, and C segregate to prior-austenite grain boundaries, whereas elements such as Cu, S, Sn, and As remain in solid solution within the matrix and do not exhibit measurable segregation at interfaces or detectable precipitation in the examined regions.

The segregation behavior in these EAF-based steels was also compared to that of conventionally produced steels from the Blast Furnace–Basic Oxygen Furnace (BF–BOF) route, providing a first assessment of how processing routes influence solid-state solute distribution. These findings provide insight into the redistribution mechanisms of residual elements in low-CO₂ PHS and their potential influence on microstructural homogeneity. This study contributes to a better understanding of how low-CO2 routes impact the nanoscale chemistry of PHS, offering guidance for alloy design and processing optimization in sustainable steel production.