Wire-Arc directed energy deposition of metastable-β alloy Ti-15V-3Cr-3Sn-3Al using thick wire feedstock: Microstructure and mechanical response

Abstract

Ti-15V-3Cr-3Sn-3Al is a metastable-β alloy initially developed to improve cold formability and reduce downstream processing costs compared to hot-forming Ti-6Al-4V. It is primarily used in sheet and welded forms, with secondary applications in castings and forgings. However, high formulation costs and strict process windows reduce expected cost benefits. This study explores an alternative manufacturing route for large-scale components using the available thick wire format (Ø3.0 mm). Ti-15V-3Cr-3Sn-3Al was deposited via plasma-based wire-arc directed energy deposition. Samples were evaluated in two conditions: (1) solution-treated (2) solution-treated and aged. Mechanical testing included tensile and hardness measurements, while microstructural analysis used a broad range of techniques. Deformation behaviour and fracture surfaces were also examined. The β-phase microstructure in the as-built condition contained α<inf>GB</inf> at grain boundaries, which dissolved during solution treatment, leaving a fully β-phase matrix. Aging resulted in the precipitation of fine α-laths, providing expected strengthening. In this condition, the material achieved an ultimate tensile strength > 1150 MPa and failure strain > 6 %, with anisotropy observed only in ductility. In the solution-treated condition, continuous softening was observed during tensile testing. This study provides insight into properties of Ti-15V-3Cr-3Sn-3Al in additive manufacturing, laying the groundwork for alternative processing routes for titanium alloys.