The influence of internal stresses on plastic instabilities in α/β titanium alloys

It is now well established that the plastic strain localization in shear bands is a natural process in the domain of large deformations. This phenomenon has been particularly studied in the last few years, especially in c.c. and c.f.c. alloys but less in h.c.p. alloys. The influence of several parameters, such as stacking fault energy, crystallographic orientation, grain size or hardening, on the nucleation and the propagation of shear bands has been largely studied. In polycrystals, it has been noted that plastic strain incompatibilities at grain boundaries promoted shear band nucleation. {alpha}/{beta} titanium alloys, which are two phase alloys, develop more plastic strain incompatibilities than the polycrystals. Also, the purpose of this work is to study the effect of these internal stresses on the nucleation and the propagation of shear bands. Besides, the plastic strain localization is not only a deformation mode but is also involved in fracture. Indeed, numerous authors have revealed that fracture could occur in shear bands. In this study, the influence of these shear bands on the fracture process under low triaxiality ({chi} < 1) will be analyzed.