Electron beam powder bed fusion (EB-PBF) is a powder-bed fusion additive manufacturing process, which is suitable for fabricating high-performance parts for a wide range of industrial applications, such as medical and aerospace. Due to its deep curing capabilities, the metastable β-alloy Ti-5Al-5Mo-5V-3Cr (Ti-5553) is currently mostly used in the landing gear of airplanes. However, its great mechanical properties make it also attractive for small, complex, and load-bearing components. In this study, nine melting parameter sets, combining different scanning speeds and beam currents, were used in the EB-PBF ARCAM A2X system. Furthermore, the correlation between the microstructure and the mechanical properties was investigated and analyzed by applying µ-focus computer tomography and microscopic methods (optical, SEM/EDS). A significant influence of the different melting parameters on the microstructure as well as on the mechanical performance was found. In a subsequent step, three melting parameters were selected and the specimens were heat-treated (BASCA, STA) for further investigation. The experimental results of this work indicate that Ti-5553 parts can be manufactured successfully with high quality (ρ > 99.60%), and post-processing heat-treatments can be used to modify the microstructure in such a way that the parts are suitable for a large variety of possible applications.

Additive manufacturing has been considered a suitable process for developing high-performance parts of medical or aerospace industries. The electron beam powder bed fusion process, EB-PBF, is a powder bed fusion process carried out in a vacuum, in which the parts are melted using a highly focused electron beam. The material class of metastable β-titanium alloys, and especially Ti-5Al-5Mo-5V-3Cr, show great potential for use as small and highly complex load-bearing parts. Specimens were additively manufactured with optimised process parameters and different heat treatments used in order to create tailored mechanical properties. These heat-treated specimens were analysed with regard to their microstructure (SEM) and their mechanical strength (tensile testing). Furthermore, in situ tensile tests, using a Deben CT5000 and a YXLON ff35 industrial µ-CT, were performed and failure-critical defects were detected, analysed and monitored. Experimental results indicate that, if EB-PBF-manufactured Ti-5553 is heat-treated differently, a variety of mechanical properties are possible. Regarding their fracture mechanisms, failure-critical defects can be detected at different stages of the tensile test and defect growth behaviour can be analysed.

Additive manufacturing (AM) is a modern way of manufacturing structures, which tends to have fewer design limitations than those manufactured by conventional processes such as casting or forging. A combination of high-strength materials and small and complex structures opens up a wide range of potential applications, especially in the fields of medicine and aerospace. Titanium and its alloys show a very beneficial combination of density and mechanical properties. One of these alloys is the metastable β titanium alloy Ti– 5Al–5Mo–5 V–3Cr (Ti-5553), which is currently used mainly for large forged structures like landing gears of airplanes. In this study, for the first time the fatigue behavior of electron beam powder bed fused (PBF-EB) Ti-5553 was investigated with a focus on the defects created by the layer wise manufacturing. To understand the defect structure and its respective influence on the fatigue behavior, all specimens were scanned prior to fatigue testing using a state-of-the-art µ-focus CT. The specimens were subjected to two heat treatment procedures commonly used in technical applications, which were aiming for high strength (solution treated and aged—STA) as well as high ductility (beta annealed, slow cooled and aged—BASCA). Results indicate that the fatigue strength of PBF-EB manufactured Ti-5553 is significantly reduced compared to conventionally manufactured Ti-5553. The main reason for this are defects, which have varying critical effects depending on the heat treatment of the specimen and the defect size, shape, location and type.