Grain boundary segregation of tramp elements and embrittlement of scrap-based green steels

Growing reliance on scrap recycling in green steel production can increase concentrations of tramp elements like Sn, Sb, Cu, and Ni, which can degrade the mechanical performance of steels. This study examines tramp element effects in a 51CrV4 steel under simulated industrial processing conditions. Alloys with varying tramp element contents were quenched and tempered at 450°C and 650°C. Atom probe tomography and high-energy X-ray diffraction, supported by density functional theory calculations, were used to establish processing-structure-property relationships.Sn, Sb, and Cu were found to segregate to grain boundaries and to be primarily responsible for impact-toughness reductions of up to 60%. No measurable difference in segregation behavior was established between random high-angle and prior austenitic grain boundaries. Density functional theory supports these findings, showing that the combined effects of Cu, Sn, and Sb on grain-boundary cohesion are more detrimental than their individual contributions. Comparison of experimentally measured segregation enrichment with first-principles segregation energies demonstrates that ab initio calculations can reliably capture low-concentration segregation trends, except for elements involving interstitial grain-boundary positions. This study provides insights into the role of tramp elements in the embrittlement of modern steels and offers guidance for mitigating their effects in future scrap-based steel production.