Impacto das variáveis de processo na solidificação e evolução microestrutural de cobre puro processado via fusão em leito de pó por feixe de elétrons

Abstract

Electron Beam Powder Bed Fusion (EB-PBF) additive manufacturing has been widely used in the production of metallic components, especially in high thermal conductivity materials such as pure copper. However, controlling solidification and the resulting microstructure is challenging, as the intense thermal gradient predominantly favors epitaxial columnar growth. Understanding the mechanisms that may promote the transition to an equiaxial microstructure is essential for optimizing the final properties of the material and expanding its applications. This study investigates the relationship between processing parameters and the microstructural evolution of pure copper in EB-PBF, focusing on layer remelting and heterogeneous nucleation as possible key factors in the transition between columnar and equiaxial growth. Variables such as melt pool depth, layer overlap, and successive thermal cycles were analyzed, along with microstructural characterization using optical microscopy and electron backscatter diffraction (EBSD). The results indicated that the predominance of the columnar microstructure may be associated with the intense thermal gradient of the process, while the transition to equiaxial grains appears to occur in regions exposed to specific remelting conditions and prolonged thermal cycles. The melt pool analysis suggests that its depth and layer overlap may influence thermal redistribution and favor heterogeneous nucleation. Furthermore, it was observed that the last solidified layers, since they do not undergo further thermal cycles, tend to maintain the columnar microstructure. Although the findings provide insights into the solidification mechanisms in EBPBF, further studies are needed to validate the proposed hypotheses. Optimizing processing parameters may enable greater microstructural control and the manufacturing of metallic parts with properties tailored to industrial needs. Future investigations exploring different scanning patterns, metallic alloys, and the impact of these variables on mechanical and thermal resistance may further expand the understanding of the subject.