Process window for electron beam melting of Ti-42Nb wt.%

Pre-alloyed beta-phase Ti-42Nb alloy was successfully produced for the first time by E-PBF. The study focuses on the determination of the processing parameter window by varying the beam current, beam speed, layer thickness, and line offset to achieve the defect-free manufacturing of new material with desired properties. Overall, 49 regimes were investigated. The Ti-42Nb powder were characterized using the DSC/TG, XRD, and SEM/EDX analyses to evaluate its suitability for E-PBF manufacturing. The alloys with the best-built quality fall into the narrow zone between the line energies of 0.30 and 0.34 J/mm. The predicted optimal process parameters were I = 4 mA, v = 700-800 mm/s, h = 100 mm, U = 60 kV, and t = 100 mm. Detailed microstructural characterization was carried out to gain insights into the fundamental mechanisms that govern the behavior of the studied alloys. TEM identified the alpha '' martensitic phase nucleation occurred preferentially at the beta grain boundaries. Un-melted ellipsoidal NbC (similar to 10 mu m) particles were detected with no preferential segregation sites. EBSD revealed coarse microstructures and <001> fiber texture, as well as epitaxial grain growth of columnar grains of about 300 mu m. The optimal regime demonstrated a texture composed of a high amount of low aspect ratio grains (50%), which yielded a microindentation hardness of 3.0 GPa and a low elastic modulus of 68 GPa. Hence, these results provide opportunities to design novel alloys to be of interest for biomedical applications. Moreover, this study extends the scope of AM by establishing the process parameter window that yields a material with favorable mechanical properties. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Pre-alloyed beta-phase Ti-42Nb alloy was successfully produced using E-PBF for the first time. The study determined the processing parameter window and provided the opportunity to design new alloys, extending the scope of additive manufacturing.