Slip transfer and deformation structures resulting from the low cycle fatigue of near-alpha titanium alloy Ti-6242Si

Abstract

Near-alpha titanium alloy Ti6242Si, widely used in aero-engine compressor discs, was subjected to low cycle fatigue loading at room temperature. Fracture initiated by facet formation, followed by striated fatigue crack growth prior to final failure. Deformation occurred primarily by planar slip, localized into slip bands in the primary alpha. Within soft-oriented grains in a microtextured region, pile-up of a slip band within one grain resulted in the direct transfer of slip into an adjacent similarly oriented grain. In contrast, pile up of dislocations in a soft grain with a ‘hard’ oriented neighbour resulted in the activation of few non-connected dislocations in the hard grain, with <a>-type dislocations being activated and the observation of cross-slip. Whilst a high density of dislocations was present from precipitation of secondary alpha in the retained beta ligaments, a little dislocation interaction was observed between the transformed beta and the primary alpha grains.