On the LFW T-Joints made via Electron Beam Melting and on the study of the Ti6Al4V powder used in the EBM process”

The Additive Manufacturing (AM) is a group of processes that allow complex shape components to be realized from raw materials in the form of powders. The compaction of the powders is achieved by local melting of bed. Electron Beam Melting (EBM) is an additive manufacturing process in which a focalized electron beam is the heat source that allows the powders to be compacted. By EBM it is possible to realize complex shape components; this feature is of particular interest in titanium industry where numerous efforts are done to develop near net shape processes. One of the limits of EBM based AM process is the difficulty to realize large dimension parts. This limit is due to the fact that the cabin, inside of which the process takes place, has maximum dimensions of 200x200x380 mm. Due to this limit the study of joining processes of different parts is of great interest. The Linear Friction Welding process has been choose because this welding technique leads to obtain joints with better mechanical properties with respect to the base material. The T-Joints have been chosen because this shape is useful both in aeronautical that in automotive field (i.e. bumpers) and because in literature a study on T-Joints obtained through LFW process has never been conducted. In the present work the microstructure evolution of sheets of TI6Al4V made by EBM and joined by Linear Friction Welding (LFW) is analyzed in details. In order to have the best performances from the LFW applied to the EBM ingots, a first experimental campaign on Traditional Ti6Al4V Joints has been conducted. The frequency and the forging force have been varied and the Traditional T-Joints have been studied in terms of ND Controls and Microstructure. The optimum LFW parameters in terms of frequency and forging force have been applied to the experimental campaign conducted on the EBM Joints. The experimental campaign conducted on the EBM Joints has been characterized by the SEM Observations. Different types of porosities have been observed inside both the base material and in the TMAZ and WZ. For this motivation, a focus on the Ti6Al4 powder used for the EBM process has been done and a full experimental campaign composed of SEM observations and statistical distribution analysis has been conducted.