Effect of Oxygen Levels in Tent Shielding Atmosphere on Microstructural and Mechanical Properties of Ti-6Al-4V Fabricated by Wire Arc Additive Manufacturing

Tent shielding is an effective and flexible method to provide inert protective atmosphere during wire arc additive manufacturing of titanium alloy. In this study, five deposited walls were fabricated by CMT-WAAM process with different oxygen levels in the tent shielding, and the influences of oxygen levels on the microstructure and mechanical properties were analyzed. The results showed that, the oscillated path provided enough time for the molten pool to absorb oxygen out of atmosphere. With the increase in oxygen level, the thickness of alpha-case with higher micro-hardness became larger, the amount of beta phase gradually decreased, the ratio of length to width for alpha lamellar was increased, and the boundary alpha phase became coarser. The higher oxygen level in the tent shielding caused an increase in tensile strength and a decrease in elongation. An ultimate tensile strength higher than 900 MPa and an elongation higher than 6% could be obtained when the oxygen level in the tent was lower than 2000 ppm.