Quantifying changes to solute segregation behaviour at interfaces in additively manufactured Ti-6Al-4V

Electron powder bed fusion has emerged as a promising additive manufacturing process for producing Ti-6Al-4V components with complex geometries. Although prior work has examined microstructural evolution phenomena including how thermal history influences the prevalence of specific α/α grain boundary misorientation intervariants governed by the Burgers orientation relationship between the α and β phases, the solute segregation behaviour at these interfaces remains poorly understood. This study employs correlative transmission Kikuchi diffraction and atom probe tomography to quantify the Gibbsian interfacial excess of V, Fe, and Al across multiple interfaces in electron powder bed fusion produced Ti-6Al-4V. V and Fe exhibited enrichment, while Al was depleted, with V segregation generally increasing with boundary misorientation. Spatial variations in segregation were observed across interface planes, although no consistent trend with boundary curvature was identified. First-principles calculations were also performed on model α/α grain boundaries to evaluate segregation energetics, confirming a thermodynamic preference for V enrichment and Al depletion. The agreement between experimental observations and DFT predictions highlights the influence of local defect structures and atomic-scale interactions on segregation behaviour. These findings improve understanding of grain boundary chemistry in additively manufactured Ti alloys and provide a basis for future grain boundary engineering approaches aimed at tailoring interfacial properties.