The use of Additively Manufactured (AM) titanium Ti-6Al-4V (Ti64) alloy has experienced a remarkable implementation for final applications in many different sectors, especially in aerospace. Ti64 belongs to the α+β family alloy. Because of the nature of the processing methodology by a layer-by-layer fabrication in Laser Powder Bed Fusion (L-PBF), a material with large internal residual stress is obtained, and with a microstructure consisting in high strength and brittle α′-phase (martensite) in the as build condition. Those aspects shall be modified by applying suitable thermal treatments (TT), with the objective of obtaining a dual α+β-phases, improving alloy ductility, and minimizing at the same time, residual stress. That means mechanical properties will be modeled during thermal treatments, looking for proper static and fatigue characteristics of the alloy according to its final application. In this case, low/high-temperature annealing treatments can be utilized, or the application of Hot Isostatic Pressing (HIP) treatments, capable of closing the remaining porosity of the alloy and increasing at the same time, the fatigue performance. Finally, surface finishing methods must be also analyzed, in order to assess their effect on fatigue performance.

The aim of this study is to evaluate the effect of different TTs in L-PBF Ti64 alloy. Microstructural features and both mechanical properties at static and fatigue level are analyzed, considering as well different surface finish treatments (e.g., machined, sandblasted, etc.). Thermal treatments have been developed at inert atmosphere conditions, with temperatures ranging from 730 to 920°C and dwell times between 2 to 4 h. Also, the effect of HIP is evaluated, by performing a two phases TT (stress relive + HIP). Finally, the evaluation of allowable for aerospace applications is analyzed against the obtained results, together with other post-processing requirements for the qualification of flight parts.