Grain boundary (GB) microstructure and chemistry significantly influence the mechanical and technological properties of engineering materials. Atom probe tomography (APT) provides sub-nm spatial resolution of 3D elemental distributions in multicomponent systems, making it an invaluable tool to study GBs. However, APT alone often lacks the ability to directly crystallographically characterise interfaces. Correlative techniques such as transmission Kikuchi diffraction (TKD) can address this limitation [1].

This study employs correlative TKD and APT to examine how GB crystallographic character and curvature affect solute segregation in Ti-6Al-4V fabricated via electron beam powder bed fusion (E-PBF). Ti-6Al-4V is widely used for its high specific strength and corrosion resistance, with E-PBF offering potential site-specific GB control via thermal history modulation [2]. Notably, five distinct α/α intervariant boundaries emerge due to the Burgers orientation relationship with the higher temperature β phase. Our results reveal that interfacial excess (Γ, atoms/nm2) varies with increasing GB misorientation: V increases, Fe remains constant, and Al decreases. Our findings provide new insights into the microstructural and chemical characteristics of these critical boundary types, to facilitate GB engineering in additively manufactured Ti alloys.

Keywords: crystallography, grain boundary, additive manufacturing, Ti alloys

References

1. A.J. Breen et al., M&M. 279-290. (2017) 23(2).
2. W.J. Davids et al., Acta Mater. 117131. (2021) 215.