Forming quality and mechanical properties of selective laser melted Ti6Al4V alloy with ultra-high scanning speed

Selective laser melting (SLM) is an advanced manufacturing technology which can directly produce fully dense near net-shaped components layer by laser from CAD models. In order to improve the building efficiency of the SLM metallic components, a novel building strategy utilizing an ultra-high laser scanning speed (above 4000 mm/s) was developed to fabricate the high-performance Ti6Al4V alloy parts. In this study, the evolution of surface morphology and porosity of Ti6Al4V alloys prepared by SLM under different ultra-high scanning speeds and other process parameters has been systemically investigated. It was found that at high scanning speeds, the defects in the samples primarily consisted of lack of fusion (LoF) defects, with their distribution closely related to the surface structure caused by material build-up. A low porosity level (0.06 %) and well machanical property (σ_UTS = 1134.08 MPa, ε = 9.50 %) could still be obtained by adjusting other process parameters, which is mainly due to an increase in the volumetric energy density (VED) reduced the number of LoF defects. Moreover, the amount of LoF defects was not wholly determined by the VED level; the surface morphology also had a significant influence on the porosity of SLM Ti6Al4V samples at a high VED level.