On the Relative Significance of Roughness, Printing Defects and Microstructure on the Fatigue Behavior of Electron Beam Melted Ti-6Al-4V

In contrast, but complementary to previous studies, this study examines the fatigue behavior in Ti-6Al-4V obtained by electron beam powder bed fusion, focusing on damage initiation sites, fatigue damage progression, and correlating these with fatigue life curves. Three material conditions were considered: as-built specimens with original surfaces after printing (AB), as-built specimens with a machined and polished surface (MP), and hot isostatic pressed specimens with a machined and polished surface (H). Fatigue fracture surface topography was analyzed using scanning electron microscopy and surface metrology microscopy. Different fatigue responses were observed, with crack initiation at surface roughness in AB, lack of fusion defects in MP, and phase facet formation in H specimens. Interaction between cracks and manufacturing defects was investigated. Kitagawa-Takahashi diagrams were applied successfully to AB and MP specimens. This study aims to enhance understanding of crack initiation and interaction mechanisms, improving life prediction capabilities through microstructure and defect-sensitive modeling.