Investigation of strain partition behavior in the lamellar microstructure of dual-phase titanium alloy based on crystal plasticity simulations

A well-designed microstructure plays a crucial part in achieving favorable properties and optimizing the service performances of titanium alloys, requiring thorough investigations of the microstructure effect on the heterogeneous deformation and strain partition behaviors. The mechanical responses of titanium alloy with lamellar microstructure are analyzed from lamellae features' crystallographic and geometric aspects through crystal plasticity simulations. It is found that the coarser β and finer α lamellae exhibited improved strain accommodation capacity which mainly benefitting from the large amount of plastic slip occurring in the coarse β lamellae of lamellar microstructure. Furthermore, the interlamellar strain partition coefficient evolves dynamically and gradually stabilizes after 5% deformation. Considering the geometric and crystallographic orientations of α phase, angles γ₁ and γ₂ are used to evaluate the strengthening effects of α lamellae precipitating from 6 types of β variants. Simulated results reveal that a more uniform strain partition occurs when cosγ₁ is in the range of 0.8–1.0 and cosγ₂ is lower than 0.3, while a higher deformation resistance occurs when cosγ₁ and cosγ₂ are in the range of 0.2–0.4 and 0.9 to 1.0, respectively. Therefore, finding an appropriate balance by manipulating the microstructural characteristics can simultaneously enhance the plasticity/strength of a titanium alloy. The obtained results will facilitate understanding the interlamellar strain partition behavior of titanium alloys and theoretically guide the microstructure designing for mechanical properties optimization.