Figure 2. Partial decomposition of α′ martensite in the thin EBM-printed Ti-6Al-4V sample.

(a) Element distribution of Ti, Al and V from views of transverse and longitudinal directions respectively in a reconstructed volume of 1 mm sample. (b) A cylindrical ROI cross over columns that delineated with iso-density surfaces of Ti + Al + V = 20 at. nm⁻¹. The columns with a higher atomic density were indicated by arrows. (c) 1D concentration profiles of all alloying elements in the ROI along the arrow direction indicated in (b). As the dense atom regions have very close compositions with initial Ti-6Al-4V ELI (see Supplementary Table 1), they were determined to be martensite. Its crystal structure was determined to be hcp in terms of SAED pattern in Supplementary Fig. 2a. Constrained α phase in α′ martensite is confirmed, indicating martensitic formation and its partial decomposition from nano scale.