Figure 4: General microstructural evolution of EBM-printed Ti-6Al-4V.

(a,b) SEM images showing martensitic microstructure at the very top area and fully decomposed α/β microstructure at the lower area of 10 mm sample. It demonstrates that martensite will form during EBM printing of Ti-6Al-4V regardless of its printing thickness. Scale bar = 5 μm. (c) Schematic illustration of microstructural evolution (prior β and α′ are in cyan, α in orange and β in blue), i.e. martensitic formation and decomposition, involved in EBM-built Ti-6Al-4V. Complexions occur at stacking faults and/or twin boundaries in α′ martensite. α phase will continuously grow at the expense of α′ and β rods appear due to the ejecting vanadium from growing α. At last, fully decomposed microstructure with β rods embedded into continuous α phase forms.