Microstructure, static properties, and fatigue crack growth mechanisms in Ti-6Al-4V fabricated by additive manufacturing: LENS and EBM

Additive manufacturing (AM) technology is capable of building 3D near-net-shaped functional parts directly from computer models using unit materials, such as powder or wire. Additive manufacturing's computer-aided design offers superior geometrical flexibility. The near-net-shaping capability also significantly reduces materials waste. These benefits make AM desirable for critical applications, such as aerospace, ground transportation, and medical. Confident utilization of the technology requires thorough understanding of the AM materials, ensuring that structural integrity and performance requirements are met or exceeded. In this study, Ti-6Al-4V fabricated by two AM techniques: Laser Engineered Net Shaping (LENS) and Electron Beam Melting (EBM) were investigated and critically compared. Samples were built using various processing parameters and heat treated under different conditions, which resulted in different microstructures and mechanical properties. Characteristic microstructures were determined for all cases. Room temperature tensile and fatigue crack growth properties were also evaluated and compared in different orientations with respect to the building direction. The effects of post-AM heat treatments on microstructure and properties were also studied. The results are systematically presented and discussed from the material/process optimization, structural design, and fatigue life prediction perspectives.