A multiscale framework for the evaluation of thermal conductivity of sintered powder at the powder bed fusion with electron beam conditions

The thermal conductivity of the powder bed during the electron beam powder bed fusion (PBF-EB) process strongly influences the process conduction and the quality of the components produced. The evaluation of this property is challenging. The models currently available in the literature cannot provide values of the thermal conductivity that consider the temperature evolution typical of the preheating step. This work presents a novel computational framework to evaluate the thermal conductivity of a powder bed for the PBF-EB process. The framework combines the thermal conditions of the PBF-EB process with information on the geometrical features of the powder bed and an analytic method to calculate the thermal conductivity and its variation with temperature and time. The proposed numerical framework is applied to the body centred structure (BCC), a typical arrangement that can emulate the PBF-EB conditions. The numerical framework is multiscale by nature, providing information about the whole powder bed starting from geometrical information about the neck among the powder particles.