High strength Ti alloy fabricated by directed energy deposition with in-situ Cu alloying

Abstract

Additive-manufactured Ti-6Al-4V has a variety of applications in the marine, energy and chemical industries. A high strength Ti-6Al-4V-8.5Cu component was fabricated by in situ Cu element using directed energy deposition technology with Cu and Ti-6Al-4V wires. The adjustment in the microstructure and performance of the obtained component was investigated afterward. The prior β grains were still columnar after Cu addition, and the intragranular microstructure was composed of Widmanstatten structure. However, the grains were significantly refined. Cu was found mainly in the solid solution in β-Ti and in nanoscale Ti 2 Cu particles between α-Ti and β-Ti. The sizes of these Ti 2 Cu particles were between 20–90 nm. Owing to the solid solution of Cu, precipitation of Ti 2 Cu particles, and grain refinement, the properties of the component were significantly improved. The average hardness of Ti-6Al-4V-8.5Cu was 370 HV 0.2 , which was 8.7% higher compared with the Ti-6Al-4V component. Furthermore, its average tensile strength was 876 MPa, which was 20.8% higher compared with Ti-6Al-4V component. The fracture morphologies of the obtained components were ductile-brittle mixed fractures. The designed Ti-6Al-4V-8.5Cu fabricated by directed energy deposition technology had improved hardness and tensile strength while retaining its plasticity. • By D-WAAM to fabricate Ti-6Al-4V-8.5Cu large components firstly. • Nano-scale Ti 2 Cu particles were only precipitated at the boundary between α-Ti and β-Ti. • Ti-6Al-4V-8.5Cu component fabricated by WAAM has improved strength while maintaining excellent plasticity.