Deformation anisotropy and heterogeneity in a Ti alloy unraveled by a crystal plasticity model with a crystallographically and spatially resolved Hall-Petch relation

This study examines the microstructural-mechanical response of a β-Ti alloy fabricated via selective laser melting (SLM) using a multi-scale framework coupling nano-to-millimeter microstructural characterization and multi-scale crystal plasticity (CP) finite element simulations. It identifies the governing mechanism by which columnar grain alignment dictates mechanical anisotropy and deformation heterogeneity. Experimentally, samples with matching inverse pole figures along the tensile loading direction (LD) show near-identical yield stresses, while samples with columnar grains oriented perpendicular to the LD exhibit higher work hardening capacity than those with grains aligned parallel to the LD. To rationalize this observed flow stress anisotropy and associated deformation microstructural features, we developed a crystallographically and spatially resolved Hall-Petch scaling law that incorporates grain shape/size effects. The model reproduces all experimentally observed trends, and relative to a conventional CP model that neglects grain shape/size effects, it predicts more heterogeneous inter- and intra-granular deformation, while also capturing grain boundary plastic strain concentration and deformation damage that is missed by the conventional model. This framework offers broad applicability for designing and predicting the performance of metallic materials with columnar grains and heterogeneous microstructures.