Influence of cooling rate on volume fraction of α massive phase in a Ti-6Al-4V alloy fabricated using directed energy deposition

[Display omitted] •Massive phase volume fraction in directed energy deposited Ti-6Al-4V was studied.•Volume fraction of massive phase was altered depending on the cooling rate.•Microstructure of massive phase was identified as fine lamellar morphology.•The formation of brittle martensite can be avoided by introducing massive phase. The relationship between the cooling rate and the volume fraction of α massive (αm) phase in a Ti-6Al-4V alloy fabricated using directed energy deposition (DED) at different powder feed rates was investigated. The results show the formation of αm phase with 1-μm-thick lamellar morphology in the built parts. The volume fraction of αm was observed to increase gradually with increasing the cooling rate; however, it decreased significantly with further increasing the cooling rate, as the martensitic phase transformation became preferable.