Effect of Processing Parameters on Defect Formation and Aluminum Content of a β-solidifying Titanium Aluminide Alloy generated by selective electron beam melting (SEBM)
Titanium aluminides are presently used in aircraft engines and are also promising materials for the application in energy technology due to their low density, high stiffness and favorable high temperature properties. However, conventional manufacturing by casting or forging is relatively cost intensive, since the low ductility of these alloys requires special strategies, such as processing above the brittle-ductile transition temperature (BDTT) for forging. Additive manufacturing can provide a suitable alternative processing route for near-net shape manufacturing of titanium aluminide components. The high preheating temperatures, which typically occur during selective electron beam melting (SEBM), can significantly improve the processability of titanium aluminides and facilitate the fabrication of complex parts. In this study, a SEBM processing window for the β-solidifying TNM™ alloy Ti-43.5Al-4Nb-1Mo-0.1B was developed. A main focus was placed on the microstructure obtained as a function of the melting parameters, such as energy density and layer thickness. In order to investigate the correlation between the processing parameters, the formation of defects and the resulting mechanical properties, both non-destructive (e. g. computed tomography) and destructive (e. g. scanning electron microscopy (SEM) on metallographic cross-sections, hardness measurements, compression tests) were applied. Moreover, the evaporation of alloying elements, especially aluminum, was thoroughly studied. The identified correlations will be discussed carefully in this contribution.