Fatigue Behavior of Aerospace Titanium Alloy Ti-6Al-4V Samples Produced by 3D Electron Beam Melting Technology

This study investigates the fatigue behavior, tensile properties, and microstructural characteristics of Ti-6Al-4V (Grade 5) specimens produced by electron beam melting (EBM). Ti-6Al-4V is widely used in aerospace, rocketry, marine, and biomedical applications owing to its high specific strength, thermal stability, and corrosion resistance. The influence of key EBM process parameters on surface quality was established across 25 parameter combinations, and as-printed specimen density was determined by hydrostatic weighing. Microstructural homogeneity was assessed through Vickers hardness mapping and SEM analysis. High-cycle fatigue tests were conducted at a stress ratio of Rₛ = 0.1, and S-N curves were constructed and compared against reference data for conventionally produced Ti-6Al-4V. While the tensile strength of as-printed material (Rₘ = 959…974 MPa, δ = 6.5…8.5%) met or exceeded the requirements for annealed Grade 5 product forms, fatigue life was found to be significantly lower under the tested process conditions — fatigue limit Δσ c,50% = 201 MPa at 2∙10⁶ cycles compared to 520 MPa for the reference material. Fractographic analysis by scanning electron microscopy identified inter-layer lack-of-fusion defects and clusters of unmelted powder particles as primary fatigue crack initiation sites, directly attributable to insufficient volumetric energy density at 100 µm layer thickness. The results demonstrate that satisfactory static strength is an insufficient qualification criterion for fatigue-critical EBM aerospace components, and that strict process parameter control is essential.