## 1 Introduction  
It has been reported that the mechanical properties of titanium and titanium alloys are greatly influenced by their microstructure [1; 2; 3]. In particular, the effect of the phase ratio, size and morphology of the \(\alpha\) and \(\beta\) phases makes it more difficult to accurately regulate their mechanical properties. By reviewing the literature, it was found that the plastic deformation of titanium alloys at room temperature included both dislocation slip and twinning [4; 5; 6; 7; 8; 9]. However, the twinning mode of duplex titanium alloys is nearly completely suppressed because of the fine microstructure and high solute contents. Therefore, dislocation slip is the dominant factor that determines the plastic deformation of duplex titanium alloys at room temperature. Dislocation slip causes slip lines and it results in a height difference on the crystal surface, with a number of slip lines constituting a slip band. Extensive studies have been devoted to slip bands in crystalline materials. For example, some studies analyzed the activation of slip systems and the slip transfer of titanium alloys at different deformation amounts based on the Electron Backscatter Diffraction (EBSD) [10; 11] method. Some works have been devoted to the understanding of the interaction between slip bands and grain boundaries in commercial pure titanium at different strain values by using high-resolution EBSD (HR-EBSD) [12]. In addition, investigations have indicated a correlation between the size of slip bands and the dislocation structure by using Atomic Force Microscope (AFM) and Transmission Electron Microscope (TEM) [13], or have identified the main slip system during plastic deformation by using AFM and Scanning Electron Microscope (SEM) [14]. However, the majority of the literature studies dealt with the slip process analysis, making only limited attempts to characterize the morphology of the slip bands, and in many cases, no clear explanations were made, such as the evolution of slip systems, the variation of stress and strain field, and the influence of grain interactions on the evolution of slip systems during the plastic deformation process. Along with the rapid development of computer software and hardware technology, the crystal plasticity finite element simulation method (CPFEM) provides the possibility of solving the above problems. It describes the mechanical behavior of different crystal orientations by adopting different constitutive parameters, and fully considers the crystal structure type, the slip system activation, the density of geometrically necessary dislocations, the hardening effect and the orientation change, which greatly increase the reliability of the analysis [15; 16; 17]. In recent years, many studies have been devoted to simulating the evolution of slip bands. [PERSON] et al. [18] proposed an approach for modeling slip bands, which qualitatively captures the experimentally observed slip band behavior of the \(\alpha\) phase in Ti-6 Al-4V by using the CPFEM to explain the slip softening due to breakdown of the short-range order between Ti and Al atoms. A local approach coupling AFM observations and polycrystal finite element calculations was proposed by [PERSON] et al. [19], which was able to determine, at the local discrete scale, the mean slip band spacing and the number of dislocations, which were helpful to further predict the environment sensitive fracture of alloys. [PERSON] et al. [20] studied slip system activation by uniaxial micro-tensile tests on single crystal ferrite samples with different orientations and demonstrated that the boundary constraints acting on the primary slip direction triggered an increase of the Schmid factors (SFs) of the activated secondary slip systems. [PERSON] et al.