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Electron beam powder bed fusion of γ-Titanium aluminide: Effect of processing parameters on part density, surface characteristics, and aluminum content

: Moritz, Juliane; Teschke, Mirko; Marquardt, Axel; Stepien, Lukas; Lopez, Elena; Brückner, Frank; Barrientos, Marina Macias; Walther, Frank; Leyens, Christoph

Fulltext ()

Metals 11 (2021), No.7, Art. 1093, 19 pp.
ISSN: 2075-4701
Deutsche Forschungsgemeinschaft DFG
212/402-1 FUGG
Focused Ion Beam Scanning Electron Microscope
Journal Article, Electronic Publication
Fraunhofer IWS ()
titanium aluminide; additive manufacturing; electron beam powder bed fusion; electron beam melting; process parameter; surface roughness; microstructure; aluminum evaporation

Gamma titanium aluminides are very interesting for their use in high-performance applications such as aircraft engines due to their low density, high stiffness and favorable high-temperature properties. However, the pronounced brittleness of these intermetallic alloys is a major challenge for their processing through conventional fabrication methods. Additive manufacturing by means of electron beam powder bed fusion (EB-PBF) significantly improves the processability of titanium aluminides due to the high preheating temperatures and facilitates complex components. The objective of this study was to determine a suitable processing window for EB-PBF of the TNM-B1 alloy (Ti-43.5Al-4Nb-1Mo-0.1B), using an increased aluminum content in the powder raw material to compensate for evaporation losses during the process. Design of experiments was used to evaluate the effect of beam current, scan speed, focus offset, line offset and layer thickness on porosity. Top surface roughness was assessed through laser scanning confocal microscopy. Scanning electron microscopy, electron backscatter diffraction (EBSD) and energy-dispersive X-ray spectroscopy (EDX) were used for microstructural investigation and to analyze aluminum loss depending on the volumetric energy density used in EB-PBF. An optimized process parameter set for achieving part densities of 99.9% and smooth top surfaces was derived. The results regarding microstructures and aluminum evaporation suggest a solidification via the β-phase.