Fracture characteristics of titanium VT1-0 and Zr–1 wt. % Nb alloy in different structures under gigacycle fatigue loading regime

Fatigue testing of ultrafine-grained, fine-grained and coarse-grained VT1-0 and Zr–1 wt. % Nb samples was performed under conditions of gigacycle fatigue regime. It was established that ultrafine-grained titanium and zirconium alloy samples initiate increasing fatigue strength of up to 1.3 times for titanium and 1.7 times for zirconium alloy within gigacycle region (109 cycles) comparable to fine-grained and coarse-grained samples. Analysis of fracture surface morphology has revealed the similar fractured structure in coarse-grained and ultrafine-grained titanium and zirconium alloy samples. Fractures in ultrafine-grained titanium and zirconium alloy samples exhibit quasi-brittle pattern

Effect of grain refinement on deformation behavior of technical grade titanium under tension

The paper deals with the study on the impact of grain refinement by severe plastic deformation upon the microstructure, as well as deformation and fracture behavior under tensile loading of technical grade titanium. The microstructure of coarse- and ultra-fine grain technical grade titanium was investigated by optical, transmission electron microscopy and X-ray diffraction. In situ monitoring of deformation behavior was conducted by means of acoustic emission and digital image correlation. Scanning electron microscopy was employed for fracture surface observation. The results of the tensile tests have revealed significant growth in ultimate strength and decrease of ductility due to grain-boundary strengthening. The experimental data obtained allow one to get the appropriate understanding of the mechanisms responsible for variation of mechanical properties and fracture patterns as well as to attain quantitative estimation of strain localization induced by the grain refinement