Crystal plasticity study on deformation behavior of dual-phase Ti alloy under biaxial loading conditions

Abstract

Titanium alloys are widely used because of their excellent mechanical properties, but the complex service environment requires a profound understanding of their deformation mechanism and mechanical behavior. The study of biaxial mechanical behavior has been plagued for decades by the inconvenience of experiments and the difficulty of ensuring the accuracy. To get a further understanding of the micromechanical behavior and corresponding deformation mechanisms of duplex titanium alloys under multiaxial loading, crystal plasticity modeling with a spectrum solver was employed in this work. The results were simultaneously analyzed using post-processing and other visualization methods to explore the disparity in deformation mechanisms between uniaxial and biaxial loading scenarios. The uniaxial tensile mechanical response of CP-Ti and Ti64 alloy were well captured using crystal plasticity modeling compared to experimental results, demonstrating both the reliability of the established model and constitutive parameters used. A strengthening effect under biaxial loading occurred owing to unique structural characteristics and mechanical constraints associated with tensile direction of hexagonal crystal structure. The region of strain bands that emerges following an increase in the biaxial ratio indicates that unbalanced biaxial stress loading can cause fracture. Prismatic slip along with basal slip predominantly governs deformation process of Ti64 alloy, while {$10\overline{1}2$} tensile twinning facilitates plastic deformation when there is limited availability of slip systems. These conclusions, on one hand, demonstrate the high-fidelity characteristic of simulation techniques and, on the other, enhance the understanding of the mechanical responses and damage mechanisms in complex service environments.