Fatigue life affected by various defects of a selective laser-manufactured Titanium alloy

Manufacturing defects introduced by selective laser melting of powder beds typically lead to lower fatigue strength and a larger scatter in fatigue life compared to conventional manufacturing methods. In this paper, the effect of build direction on the low cycle fatigue performance of laser powder bed fused Ti6Al4V alloy was studied. Tests under room temperature were conducted and fractographies were examined to identify the crack initiation source. Results show that fatigue cracks in all samples initiated from sub-surface pores. The roundness of pores was proved to have an influence on fatigue life. Therefore, pores were assumed as existing cracks and its roundness was used to modify a fracture mechanic-based life prediction model.