Fatigue Behavior and Failure Analysis of Ti-6Al-4V Forging with High Oxygen Content

The microstructure, texture and HCF (high cycle fatigue) behavior of a Ti-6Al-4V forging with 0.20 wt% oxygen were investigated. The material was composed of 80 vol% of equiaxed alpha(p) grains and 20 vol% of transformed beta (beta(T)). Average size of the alpha(p) phase was about 14 mu m. EBSD analysis indicated a weak basal texture with intensity of 2 times random. The forging billet exhibited a good combination of ductility and strength performance and the mechanical properties did not show obvious anisotropy. The fatigue life had a large scatter and the mean life increased as the stress level decreased. The minimum life and POF = 0.1% life of the samples increased with the decrease of stress level. The difference of the feature of facets at the fatigue crack initiation region is considered to be the main cause of fatigue life scatter. The formation of the faceted area in fatigue crack initiation area results from the nucleation site of fatigue crack located in grain clusters with similar orientation.