On the relative significance of roughness, printing defects and
microstructure on the fatigue behaviour of electron beam melted
Ti-6Al-4V
Abstract
In contrast, but complementary to previous studies, this study examines
the fatigue behaviour 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 analysed
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
modelling.