Development of directed energy deposition strategy for a mechanically interlocked pure Ti and Al alloy component with cross-shaped internal pure Ti lattice

Abstract

Directed energy deposition (DED) using multi-metal materials typically employs a metallurgical bonding approach. The components using titanium (Ti) and aluminum (Al) alloys have attracted significant interest in aerospace and automotive industries due to their ability to decrease fuel consumption through lightweight construction. However, DED using Ti and Al alloys that are difficult to fusion-bond is plagued by the formation of brittle intermetallic compounds. In particular, the deposition of a Ti alloy layer on that of Al alloy decreases the mechanical property of the entire component. This study developed a DED strategy using wire and arc discharge for the mechanical interlocking of pure Ti ERTi-2 and Al alloy ER5356. First, the effects of heat input, fabrication paths, and arc locations on the interface and composition of the adjacent beads were clarified. A fabrication strategy was developed to achieve the desired fusion state and avoid collision between welding torch-fabricated component. A mechanical interlocked component with an internal ERTi-2 cross-shaped lattice and planar ERTi-2 surface layers was successfully fabricated. In addition, these results demonstrate that the developed fabrication strategy can be applied to the other metal combinations that are difficult to fusion-bond. Subsequently, X-ray computed tomography clarified that the internal ERTi-2 lattice was fabricated in the target geometry. Tensile tests were carried out using the mechanical interlocked components with an internal cross-shaped unit lattice. The yield and ultimate tensile strength were 45.1 ± 3.4 MPa and 55.5 ± 4.6 MPa, respectively. These values and the fracture positions were in good agreement with the predictions from the mechanical properties of the used materials and the lattice geometry. Hence, this study underscores the potential of mechanical interlocking to improve the mechanical properties of the multi-metal components that pose challenges for fusion-bonding.