In-situ characterization of twin nucleation and correlated crystal plasticity modeling of deformation behavior in alpha titanium using 3D X-ray diffraction data

The goal of this study is to gain a clearer understanding of the conditions that favor nucleation of T1 twinning in commercial purity titanium. A tensile specimen with a strong c-texture was deformed to about 2% global strain. Concurrently, far field 3D X-ray diffraction from the synchrotron source at the APS was used to identify type 1 (T1) deformation twinning events. Identification of the twin-parent grain pairs was done using criteria for c and a axes misorientation and spatial proximity. Two approaches are used to assess the geometrical plausibility of a twin resulting from slip transfer (S+T); or twin induced shear transfer (T+T) across a grain boundary. The first step involved calculation of the slip transfer parameter. Second, the relative elevation (along the tensile direction) of the parent grain with respect to the adjacent grain(s) is examined. In addition, Voronoi tessellation is used to generate a representative volume element of the microstructure. Local stress–strain data from a spectral crystal plasticity based model is compared to experimental values, to identify local stress states associated with nucleation of a twin