Influence of Electron Beam Powder Bed Fusion Process Parameters at Constant Volumetric Energy Density on Surface Topography and Microstructural Homogeneity of a Titanium Aluminide Alloy

• Published in: Advanced engineering materials 2023-08, Vol.25 (15), p.n/a
• Main Authors: Moritz, Juliane, Teschke, Mirko, Marquardt, Axel, Stepien, Lukas, López, Elena, Brueckner, Frank, Walther, Frank, Leyens, Christoph
• Format: Article
• Language: English
• Subjects: additive manufacturing; aluminum evaporation; electron beam powder bed fusion; heat treatments; Manufacturing Systems Engineering; process parameters; Produktionsutveckling; titanium aluminides
• ISSN: 1438-1656; 1527-2648; 1527-2648
• DOI: 10.1002/adem.202201871

In powder bed fusion additive manufacturing, the volumetric energy density E V is a commonly used parameter to quantify process energy input. However, recent results question the suitability of E V as a design parameter, as varying the contributing parameters may yield different part properties. Herein, beam current, scan velocity, and line offset in electron beam powder bed fusion (PBF‐EB) of the titanium aluminide alloy TNM–B1 are systematically varied while maintaining an overall constant E V. The samples are evaluated regarding surface morphology, relative density, microstructure, hardness, and aluminum loss due to evaporation. Moreover, the specimens are subjected to two different heat treatments to obtain fully lamellar (FL) and nearly lamellar (NLγ) microstructures, respectively. With a combination of low beam currents, low‐to‐intermediate scan velocities, and low line offsets, parts with even surfaces, relative densities above 99.9%, and homogeneous microstructures are achieved. On the other hand, especially high beam currents promote the formation of surface bulges and pronounced aluminum evaporation, resulting in inhomogeneous banded microstructures after heat treatment. The results demonstrate the importance of considering the individual parameters instead of E V in process optimization for PBF‐EB. Different combinations of beam current, scan velocitiy, and line offset at constant energy density in electron beam powder bed fusion of a titanium aluminide alloy are investigated. While even surfaces and homogeneous microstructures are achieved with some parameter combinations, others cause pronounced aluminum evaporation and swelling, indicating that the parameters should be optimized individually rather than considering only energy density.