Equiaxed (Mill Annealed) Ti-6Al-4V

Summary

The equiaxed microstructure of Ti-6Al-4V is achieved through the mill annealed processing route, where a cold-rolling processing step introduces regions where many grains have similar crystallographic orientations. These “microtextured regions” (MTRs) are visible in results obtained from electron backscatter diffraction (EBSD) experiments (both 2D and 3D). Further experiments provide insight on the initiation of slip activity, and also show that MTRs have a pronounced impact on the localization of plastic deformation before the onset of macroscopic yield.

The measured orientations from EBSD experiments are used to construct a functional representation of the orientations present. These orientation distribution functions are used to select orientation sets for representative polycrystals for use in simulations. A suite of simulations is performed on sets of polycrystals with and without MTRs. Additionally, the initial strengths of the various slip families witnessed to be active during the onset of slip are altered to determine their impact on the initiation of slip.

Results from the simulations showed that the localization of plasticity witnessed in experiments is only captured when including the MTRs in the polycrystal. The relatively early localization of plasticity is important, as the simulations performed without MTRs have homogeneous plasticity across the polycrystal – even though both agree in terms of the onset of slip activity. This early localization has effects on the overall ductility of the material. The results are also sensitive to the initial slip strengths of the slip families, and best match the experimental results when using values that agree with contemporary literature.

Collaborators

McLean P. Echlin, University of California Santa Barbara.
Jean-Charles Stinville, University of California Santa Barbara.
Tresa M. Pollock, University of California Santa Barbara.
Paul Dawson, Cornell University

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