Minimizing the buy-to-fly ratio of aircraft structural parts made from milled Ti-6Al-4V is an important step in reducing the environmental impact of the aerospace industry. One possible way to achieve this goal is through wire and arc additive manufacturing (WAAM), an additive manufacturing technique based on arc welding. It is a cost-effective process with a minimal lead-time and significantly reduces material waste through near-net-shape manufacturing. In previous investigations, we determined the most relevant WAAM-process parameters and developed an in-depth understanding on the process-parameter-microstructure-properties correlation [1-3] with a focus on understanding the thermal management and its influence on the intrinsic heat treatment.

Due to titanium’s low heat conduction, heat accumulates and further reduces the cooling rate. This leads to elongated β-grain growth and thus anisotropic properties. Additionally, titanium’s affinity to oxygen has to be taken into account during the manufacturing process to avoid α-case formation. In this work, samples with two different cooling rates achieved by using air curtains as well as three further samples produced with different residual oxygen content are investigated. The aim is to establish a correlation between process parameters, microstructure and mechanical properties. The samples were analyzed in terms of their microstructure and mechanical properties using Scanning Electron Microscopy, tensile and compression tests as well as nanoindentation.

Effects of the varying cooling rates as well as the impact of higher residual oxygen contents on the microstructure and mechanical properties were evaluated. These results highlight the importance of comprehensively understanding the impact of both thermal management and atmosphere on the production of Ti‑6Al‑4V components.



References
[1] D. Elitzer et al. MATEC Web of Conferences, 2020, 321, 03037.
[2] D. Elitzer et al. Advanced Engineering Materials, 2022, 25, 2201025.
[3] C. Fuchs et al. Production Engineering, 2023, 17, 703-714.