Microstructure and Mechanical Property Evolution of TC4 Titanium Alloy During Cold Drawing

ABSTRACT

This study investigates microstructural evolution and mechanical properties of TC4 wires during multi‐pass cold drawing and annealing. Starting from a φ8.5 mm rod, wires were skin‐passed to φ8.0 mm and drawn to φ6.0 mm. EBSD reveals that drawing increases strength by ∼25% while reducing ductility, with fibrous grains, high dislocation density estimated from KAM, and increased low‐angle grain boundaries. The special Σ33c boundary fraction drops from > 17% to near zero, disrupting this coherent toughening network. Annealing after medium deformation (φ7.0 mm) yields optimal strength‐ductility synergy, attributed to optimal stored energy distribution that completely disrupts original Σ33c boundaries and drives uniform recrystallization without excessive grain growth. New special boundaries (e.g., Σ11) form upon annealing. This clarifies low‐energy boundary transformation and establishes process‐microstructure‐property relationships for grain boundary engineering of TC4 wires.