A three-dimensional microstructure-based crystal plasticity model for coarse-grained and harmonic-structured Ti–6Al–4V under monotonic and cyclic shear loading

This paper develops a microstructure-based numerical model to simulate the mechanical behavior of homogeneous coarse-grained (CG) and harmonic-structured (HS) Ti–6Al–4V under monotonic and cyclic simple shear loading conditions. This model incorporates a crystal plasticity model describing the deformation behavior of lamellar $\alpha +\beta$ colonies and a scale transition rule called '$\beta$-rule' which enables to deal with the huge contrast between grain sizes in fine-grained and coarse-grained regions in HS Ti–6Al–4V. Besides, the numerical model can be used to consider the effects of microstructural features, such as the slip geometry for lamellar $\alpha +\beta$ colonies, length scale dependence of hardening, or anisotropic strength of the slip systems. The model is implemented into a finite element code (Cast3M) via a UMAT subroutine. The strengthening effect of harmonic structure design is studied based on the numerical results for HS Ti–6Al–4V and homogeneous CG Ti–6Al–4V. The simulation results are in good agreement with the experimental observations.