Electron Beam Powder Bed Fusion (PBF-EB) is enabling the processing of brittle high temperature alloys. The material class of γ-Titanium Aluminides (γ-TiAl) is one example, which is prone to aluminium evaporation. On the one hand, this is an opportunity to control the microstructure [1]. On the other hand, it is challenging to predict the concentration loss during the process. In this study, a part-scale evaporation model is proposed to be able to predict the concentration- and energy-loss within a purely thermal model. Based on the physics of evaporation and an established mesoscale model [2], a coarse model is derived. First calculations on a fine scale revealed the local concentration depletion on the surface as a limiting factor for evaporation of volatile elements. An iterative analytical model is used to account for the sublattice concentration profile on the macroscale. The temperature-dependent diffusion coefficient is utilized as a modelling parameter to map the neglected effects like convection and surface deformation by the recoil pressure. The proposed model was applied to PBF-EB built samples of the γ-TiAl alloy Ti-44.5Al-4Nb-1Mo-0.1B (TNM) from literature [3]. Compared to models transferred one-to-one from the mesoscale to the macroscale, the developed approach shows a significantly higher accuracy, matching the experimental values for various parameters. The novel part-scale evaporation model can be applied to develop scan strategies for microstructure control of alloys with volatile elements. Furthermore, the accuracy of thermal part-scale models can be increased due to the improved evaporation energy loss calculation. REFERENCES [1] Knörlein, Julia; Franke, Martin Michael; Schloffer, Martin; Körner, Carolin: In-situ aluminum control for titanium aluminide via electron beam powder bed fusion to realize a dual microstructure. Additive Manufacturing. (2022) 59:103132. https://doi.org/10.1016/j.addma.2022.103132 [2] Klassen, Alexander; Forster, Vera E.; Körner, Carolin: A multi-component evaporation model for beam melting processes. Modelling Simul. Mater. Sci. Eng. (2017) 25 (2):25003. https://doi.org/10.1088/1361-651X/aa5289 [3] Reith, M.; Franke, M.; Körner, C. Impact of the acceleration voltage on the processing of γ-TiAl via electron beam powder bed fusion. Prog Addit Manuf. (2024) 9 (5): 1425–1436. https://doi.org/10.1007/s40964-023-00499-4