Enhanced Fatigue Strength of Ultrafine-grained Ti-6Al-7Nb ELI Alloy: Microstructural Aspects and Failure Peculiarities

摘要

This paper deals with the cyclic deformation behavior of the ultrafine-grained (UFG) Ti- 6Al-7Nb alloy with extra low content of impurities (ELI) produced by severe plastic deformation (SPD). The SPD processing comprised equal channel angular pressing (ECAP) and subsequent thermomechanical treatment and was aimed at improvement of mechanical properties of the alloy. Formation of a UFG structure with the average a phase grain size of 250 ± 50 nm led to enhancement of fatigue endurance limit by 40% as compared to the coarse-grained state. The presented microstructural investigations demonstrated that the UFG microstructure significantly influences the crack paths and is very stable in the course of cyclic deformation. A high potential for prospective use of the UFG alloy in biomedical and engineering applications was discussed.