Abstract
Heterogeneous deformation, including local dislocation shear activity and lattice rotation, was analyzed in microstructure patches of polycrystalline commercial purity titanium specimens using three different experimental methods. The measurements were compared with crystal plasticity finite element (CPFE) simulations for the same region that incorporate a local phenomenological hardening constitutive model. The dislocation activity was measured using techniques associated with atomic force microscopy (AFM), confocal microscopy, three-dimensional-X-ray diffraction (3D-XRD), and nano-indentation. These measurements allow assessment and guidance for strategic improvement of the accuracy of CPFE model development. The CPFE model successfully predicted most types of active dislocation systems within grains at the correct magnitudes, but the simulation of spatial distribution of strain was not always similar to experimental observations. To obtain an accurate CPFE model, the critical resolved shear stresses for major deformation systems in -titanium were assessed using an optimization strategy with CPFE predictions of the measured pile-up topography surrounding axisymmetric nano-indentation. Only modest improvements were noted over the simulations done without such optimized parameters. This indicates that a major challenge for model development is to effectively predict conditions where slip transfer occurs, and where geometrically necessary dislocations (GND) accumulate.