| Abstract Scope |
This study presents the fabrication and characterization of bimetallic TZM–Ti6Al4V (Ti64) thin-wall structures produced using Wire Arc Additive Manufacturing (WAAM). The objective was to evaluate the feasibility of joining a refractory molybdenum-based alloy (TZM) with a titanium alloy (Ti64) and to assess the resulting microstructural, mechanical, and corrosion properties of the multi-material system. Optical microscopy and scanning electron microscopy (SEM) revealed the formation of a continuous and defect-free metallurgical interface, free from cracks, porosity, and other processing-induced defects. A narrow transition region was observed at the interface, indicating limited elemental diffusion and effective metallurgical bonding between the dissimilar alloys. Microhardness measurements demonstrated a clear variation across the bimetallic structure. The TZM substrate exhibited relatively uniform hardness values ranging from 225 to 235 HV, whereas the Ti64 deposit showed significantly higher hardness values between 340 and 385 HV. A localized hardness reduction was observed near the interface, followed by a sharp increase within the Ti64 region, reflecting the influence of compositional gradients and microstructural evolution across the transition zone. The absence of excessive hardness peaks suggests that no brittle intermetallic phases formed during deposition. Mechanical testing indicated that the fabricated structure exhibited continuous strain hardening behavior, achieving an ultimate tensile strength of approximately 330 MPa and a total elongation of about 7.5%. Fracture occurred after substantial plastic deformation, indicating a favorable balance between strength and ductility. Electrochemical corrosion testing showed that Ti64 possessed the highest corrosion resistance, while TZM exhibited the highest corrosion rate. The TZM–Ti64 bimetallic structure displayed intermediate corrosion behavior, with improved corrosion resistance compared to TZM due to the presence of a sound metallurgical interface and stable passive oxide films. Overall, the results demonstrate the feasibility of producing TZM–Ti64 multi-material structures by WAAM for potential high-temperature and structural engineering applications. |