Elastic plastic deformation of TC6 titanium alloy analyzed by in-situ synchrotron based X-ray diffraction and microstructure based finite element modeling

Abstract

The phase properties and distribution of multi-phase materials not only produce heterogeneous stress distributions between phases, but also stress gradients inside grains. However, due to limitations of stress/strain partitioning at the submicron scale, mechanical property characterizations of such alloys are typically based on evaluating averaged responses, e.g. macroscopic stress-strain curves. Here, the elastic plastic deformation of α/β dual phase TC6 titanium alloy is investigated in depth on the microstructural level by a two dimensional microstructure based finite element method (FEM). In-situ synchrotron based X-ray diffraction was also used to characterize the lattice strain evolutions during deformation. The microscopic stress and strain evolutions were successfully tracked by FEM during the elastic plastic transition process. The α phase bears a relatively high stress compared to the β phase during the elastic deformation stage. In the elastic to plastic deformation stage, a stress inversion phenomenon was observed in the microstructure by path tracing to elucidate the stress transfer process in detail. In the plastic deformation stage, strong plastic strain concentration occurs in the α phase near phase boundaries. The current local strains and stresses of α and β phases are not synchronous with the applied macroscopic true strains and the corresponding constitutive stresses. Moreover, different current local strain rates produce obvious stress gradients inside the α grains.