Modeling Strain Localization in Microtextured Regions in a Titanium Alloy: Ti–6Al–4V

Abstract

Large and highly textured regions, referred to as macrozones or microtextured regions, with sizes up to several orders of magnitude larger than those of the individual grains, are found in dual-phase titanium alloys as a consequence of the manufacturing process route. These macrozones have been shown to play a critical role in the failure of titanium alloys, specifically being linked to crack initiation and propagation during cyclic loading. Modeling microstructures containing macrozones using continuum-level formulations to describe the elastic–plastic deformation at the grain scale, i.e., crystal plasticity, poses computational challenges due to the large size of the macrozones, which in turn prevents the use of modeling approaches to understand their deformation behavior. In this work, a crystal plasticity-based modeling approach is implemented to model macrozones in Ti–6Al–4V. Further, to overcome the large computational expense associated with modeling microstructures containing macrozones, a modeling strategy is introduced based on a crystal plasticity description for the macrozone with a reduced-order model for the surrounding aggregate combining anisotropic elasticity and J2 plasticity, based on crystal plasticity-based training data. This modeling approach provides a grain-level description of deformation within macrozones using elastic–plastic continuum simulations, which has often been overlooked. Finally, the reduced-order model is used to investigate the strain localization within the microstructure and the effect of varying the misorientation tolerance on the localization of plastic strain within the macrozones.