Low- and high-cycle fatigue resistance of Ti-6Al-4V ELI additively manufactured via selective laser melting: Mean stress and defect sensitivity

Selective laser melting (SLM) is a net-shape AM technology to produce metal parts also for load-carrying applications. The present work is aimed at investigating the fatigue performance of the biomedical titanium Grade 23 (aka Ti-6Al-4V ELI) AMed via SLM. Low and high cycle fatigue tests are carried out on samples that received a low temperature stress-relief treatment. In addition, the effect of selected post processing treatments on the high cycle fatigue response is assessed. Material characterization is complemented with residual stress and microhardness measurements, computed tomography scans, metallographic and fractographic inspections. These experimental analyses served to elaborate an interpretative model accounting for the modifications produced by the post-processing treatments. The results denote the important role exerted by mean and residual stresses as well as defects on the fatigue performance. The relatively low fatigue strength of SLM manufactured parts indicates that further developments in this fabrication route are still necessary to make their mechanical properties competitive with those of traditionally processed components.