High strain rate response of CP-titanium under low-temperature conditions: experiment and modeling

Abstract This study investigates the dynamic mechanical behavior and microstructural evolution of commercially pure titanium (CP-Ti) under high-strain-rate loading at subzero temperature. Using a Split Hopkinson Pressure Bar setup equipped with a cryogenic environmental chamber, CP-Ti specimens were dynamically compressed at − 100 °C across strain rates of 1 × 10 3 s −1 and 2 × 10 3 s −1 . The results show a significant increase in flow stress at − 100 °C compared to room temperature, with peak true stresses reaching approximately 825 MPa at 2 × 10 3 s −1 and 730 MPa at 1 × 10 3 s −1 representing ~ 25–30% higher values than those observed at 22 °C. Electron backscatter diffraction analysis revealed a transition in deformation mechanisms with increasing strain rate and decreasing temperature. At room temperature, plastic deformation was predominantly accommodated by dislocation slip and deformation twinning. At low temperature, while twinning activity intensified, it was eventually superseded by shear band formation, indicating the onset of strain localization. A physically based viscoplastic constitutive model incorporating dislocation density evolution and thermally activated mechanisms was developed and calibrated against experimental data. The model accurately captured the stress–strain behavior across all tested conditions, with deviations below 5%, demonstrating its suitability for predictive simulations of low-temperature forming processes in HCP metals.