On slip initiation in equiaxed α/β Ti-6Al-4V

A computational study of 3D virtual instantiations of microtextured Ti-6Al-4V with varying initial slip system strengths is presented. Electron backscatter diffraction (EBSD) scans of a rolled and heat-treated mill annealed plate were used in order to determine the approximate geometric morphology of both the grain structure and the microtextured regions. Data from the EBSD experiments were used to calculate representative orientation distribution functions (ODFs) and grain size distributions for the α (HCP) crystallographic phase. Laguerre tessellations were employed to create idealized geometric representations of the microstructure and microtextured regions, while orientations were sampled from the experimentally derived ODFs. A highly parallelized crystal plasticity finite element framework was used to model the deformation response of single phase polycrystals under uniaxial tension, with attention paid to the intragrain slip system activity. Simulations were conducted with changes in the orientations within microtextured regions, as well as with various sets of initial slip system strengths to reflect differences in reported values in literature. Results were compared to a strength-to-stiffness parameter designed to predict succession of yield as a function of orientation. Presented are slip activity trends as a function of microstructure and initial slip system strengths, as well as results concerning the development of long-range localization of plasticity as a function of the microstructure. Predictions are compared to slip system activity measured by scanning electron microscope based digital image correlation.

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