Investigation of microstructures, defects, and mechanical properties of titanium-zirconium-molybdenum alloy manufactured by wire arc additive manufacturing

Titanium‑zirconium‑molybdenum (TZM), one of the refractory alloys, has extraordinary physicochemical properties, making it ideal for usage in extreme environmental applications (e.g., high-temperature and nuclear). Due to the scalability and near-net shape fabrication, metal additive manufacturing processes have several advantages, leading it to be the possible solution for the fabrication of refractory alloy structures. Wire arc additive manufacturing (WAAM) has several advantages, including high deposition rate, energy efficiency, and cost-effective manufacturing of large components. In this study, we comprehensively investigated the relationships among process, microstructures, mechanical properties, and defects of TZM thin-walls manufactured by WAAM using four heat input conditions: 180A, 200A, 220A, and 240A. The microstructures were investigated using multi-scale material characterization techniques. Columnar grains were generated along the build direction, and carbide precipitates were found uniformly distributed in the Mo matrix. Multi-scale pores and cracks were present in the microstructures. The average microhardness values for the deposits ranged from 188.5 to 193.5 hardness scales of Vickers. The highest yield strength, 195 MPa, was found in the 200A heat input condition. The primary fracture mode was identified as a brittle transgranular. The area fraction of porosity was calculated >1% in each condition, with the largest being 2.04% in the 240A deposit.