Mechanical behavior of course-grain and ultrafine-grain titanium for biomedical application

摘要

The manuscript is devoted to the investigation of microstructure, static and fatigue tensile properties of commercially pure titanium grade 2 in two states with coarse grains (CG ≈ 25 μm) and ultra-fine grains (UFG ≈ 0.2 μm). During mechanical tests, the in situ monitoring was conducted by means of acoustic emission and digital image correlation. Scanning electron microscopy was employed for fracture surface observations. The results of the tensile tests show significant growth in ultimate strength and decrease of ductility due to grain-boundary strengthening. Fatigue tests revealed that the high amount of defects (grain boundaries, dislocations, etc.) in UFG suppress plastic deformation and leads to earlier crack initiation, however, at the macrocrack growth stage, these impurities are obstacles for the transgranular mechanism of fracture. The experimental data obtained allow one to get the appropriate understanding of the mechanisms responsible for the variation of mechanical properties and fracture patterns as well as to attain quantitative estimation of strain localization induced by the grain refinement.