Main Microstructural Characteristics of Ti-6A1-4V Components Produced via Electron Beam Additive Manufacturing (EBAM)

摘要

Electron Beam Additive Manufacturing (EBAM) is a Wire Directed Energy Deposition (W-DED) process that is receiving much more attention than other Additive Manufacturing (AM) techniques, especially in the aeronautical sector for the serial production of metallic parts. However, this technique leads to singular microstructures due to the rapid heating and cooling cycles generated during the deposition of the pieces. In this work, a first identification of the main microstructural features of Ti-6Al-4V parts manufactured by EBAM technology is performed to better understand the general characteristics of this type of parts for further improvement of this technology. The characterization is carried out by means of Optical Microscopy (OM), Scanning Electron Microscopy (SEM) observations, and Energy Dispersive X-Ray Spectrometry (EDS) analysis. The most remarkable aspects found are the formation of long columnar prior beta grains throughout several layers in the built material and the presence of many parallel thermal bands perpendicular to the thermal gradient. Quantitative measurements such as the average width of the α lamellae, the volume fraction of β phase, and the chemical composition at different positions are also accomplished. A heterogeneous microstructure is reported, which mainly derives from the complex and diverse thermal histories at the different positions of the deposited material. In addition, Al vaporisation is noticed. However, no significant change along the deposit material is observed for a same configuration. Next, experiments will focus on the influence of different key processing parameters on the microstructure and mechanical properties.