Secondary twinning–mediated anisotropy in ultra-thin commercially pure titanium (CP-Ti) sheets: A crystal plasticity approach

초록

This study investigates plastic deformation-induced anisotropy and its corresponding microstructural evolution in an ultra-thin Grade 1 commercially pure titanium (CP-Ti) sheet subjected to uniaxial tension along different loading orientations. Experiments reveal pronounced anisotropy not only in mechanical response, but also in twinning activity and texture evolution. Tensile loading along the rolling direction (RD) leads to the formation of tensile twins identified as secondary twins nucleated within pre-existing compressive twins, resulting in complex crystallographic reorientation. In contrast, transverse direction (TD) tension is characterized by gradual narrowing of the {0001} pole toward the normal direction (ND). To capture these behaviors, we extend an established crystal plasticity finite element (CPFE) formulation based on conventional slip and pseudo-slip twinning kinetics by introducing a multi-sectional internal representation that independently evolves the constitutive states of the matrix and multiple twin variant sections and permits further twinning within each activated twin section. The model successfully reproduces the experimentally observed anisotropy and demonstrates that explicit modeling of secondary twinning along with primary twinning is important for capturing the texture evolution. The model was further assessed under diagonal direction (DD) tension, providing an additional validation of its applicability beyond the principal loading directions. The proposed framework provides a crystallographically informed and computationally efficient tool for predicting anisotropic deformation and twinning-mediated microstructural evolution in hexagonal close-packed metals. © 2026 Elsevier Ltd.

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