Microstructural, Mechanical and Corrosion Performance of NbZr1-Ti64 Multi-Material Structure Fabricated via Wire Arc Directed Deposition.

This study investigates the fabricability, microstructures, and mechanical and corrosion behavior of a multi-material structure (MMS) composed of niobium alloy (NbZr1) and titanium alloy (Ti64) using a wire arc directed energy deposition process. The microstructure of NbZr1 alloy primarily consisted of equiaxed grains oriented in the rolling direction, while the deposited Ti64 microstructure exhibited 'banding' morphology and a basket-weave structure composed of α phase lamellae in a β matrix. The MMS interface revealed good metallurgical bonding and was free from defects such as cracks, pores and intermetallic phases. Niobium diffusion from NbZr1 into the Ti64 alloy resulted in the formation (β-Ti + Nb) of a solid solution which imparted strength to the MMS. Hardness testing showed that microhardness values follow the following trend: NbZr1 substrate > MMS interface > Ti64 deposit. The NbZr1-Ti64 multi-material structure developed in this study exhibited a balanced combination of ductility (22.73% elongation) and moderate tensile strength (254.18 MPa), outperforming most reported NbZr1-Ti64 MMS studies. All tensile specimens failed in a ductile manner on the NbZr1 side. The MMS demonstrated superior corrosion resistance, exhibiting the lowest corrosion current density and corrosion rate compared to its individual counterparts.