Effects of Triaxiality and Microstructure on Ductile Fracture of alpha/beta Titanium Alloys

摘要

The effects of microstructure and Triaxiality on ductility were investigated for alpha/beta Titanium alloys with equiaxed alpha phase. The materials tested were Ti-6Al-4V, Ti-4.5Al-3V-2Fe-2Mo and Ti-10V-2Fe-3Al, and several different heat treatments were conducted for these materials to obtain the different grain size and morphology. It was shown that the most of micro-voids in alpha/beta titanium alloys were nucleated at alpha/beta interface, and the microstructural parameter defined as the average distance between alpha/beta interfaces was closely related to the dimple size on the fracture surface. The refinement of microstructure leads to the reduction of ductility, though near-beta titanium alloys with ultra-fine particle have exceptionally a different tendency from other materials. The dependency of Triaxiality on fracture strain obtained in the round bar specimens were also investigated. Significant reduction of strain with the increase of Triaxiality is observed, but the reduction due to the high Triaxiality is different in each materials. It is shown that the void growth strain in higher strength materials is relatively small, and it results small dependency of the Triaxiality on the ductility.