Crystal Plasticity Finite Element Method for Slip Systems Evolution Analysis of α/β Duplex Titanium Alloys during Quasi-Static Tensile Testing

The crystal plasticity finite element method, modeled on a realistic microstructure image, was developed to investigate the evolution of slip systems in grains of α/β titanium alloys during quasi-static tensile testing. By analyzing the data of slip evolution of simulation during the overall plastic deformation process, it was found that the prismatic slip systems in the α phase and the {112} <111> slip systems in the β phase played a leading role. By calculating the Schmid factors, it was found that the values calculated from the local stress, which was represented by major principal stress, were larger than the values calculated from the primary uniaxial tensile direction, which was due to the deviation of the local stress direction from the primary uniaxial tensile direction. Furthermore, the deviation of local stress of α phase was different from that of β phase, which was related to the deformation mechanism. During the deformation, the stress and strain were concentrated in the grains of the α phase, producing a driving effect on the neighboring grains of the β phase. Subsequently, the incompatible deformation produced the concentration of strain at the grain/interphase boundary, thus strengthening the grain interactions and leading to the deviation.