Oxidation induced mechanisms during directed energy deposition additive manufactured titanium alloy builds

•Oxidation during out of chamber DED Ti6242 occurs concurrently in the liquid and solid state.•Oxygen species reverse the Marangoni force, causing centripetal flow, deepening the molten pool and assisting pore escape.•Oxygen can promote the formation of tetra modal α phase microstructure in Ti6242.•The α-phase Ti6242 alloy is more resistant to oxygen diffusion than Ti-6Al-4 V as SiO2 inhibits TiO2 formation.•New DED-AM industrial practices can be adopted to tailor ti alloys microstructure (texture, phases, and porosity).