Effect of recycled powder content on the structure and mechanical properties of Ti-6Al-4V alloy produced by direct energy deposition

Abstract Direct energy deposition (DED) is a promising additive manufacturing technique in the area of aerospace, automotive, shipbuilding and medical industries. DED allows producing large-scale parts that imply the use of a significant amount of powders. Powder reuse is an important task that leads to a reduction in the cost of the final parts. In this work, Ti-6Al-4V samples were fabricated by DED with a mixture of unused and recycled powders in the recycled powder content of 0%, 10%, 25%, and 50%. The results show that the morphology of the powder does not change significantly due to a low number of powder uses. Chemical analysis reveals a slight decrease of V in the recycled powder. The evolution of macrostructure with increasing recycled powder content was not revealed. In the as-built samples, the columnar prior β grains grow toward the build direction with a typical Widmanstatten structure consisting of the thin α' laths. The mix of Widmanstatten microstructure and basket weave microstructure appears after the annealing at 800 ℃. Samples with 50% recycled powder demonstrate the more pronounced α+β phase composition after the annealing. Furthermore, the horizontal and vertical annealed samples exhibit ductile fracture and inconspicuous anisotropy of tensile and impact mechanical properties.