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

Abstract 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.