Low temperature mechanical-dynamical behavior of commercially pure titanium under different thermal treatments

This research investigates the dynamic mechanical properties of Commercially Pure Titanium (CP-Ti) Grade 2, the relationship between its thermo-mechanical history, resulting microstructure, and anelastic behavior using the Mechanical Spectroscopy (Internal Friction) technique, supplemented by Transmission Electron Microscopy (TEM) and standard tensile testing, across four industrially relevant material states: the as-received (cold-worked) condition, stress-relieved (560 °C), fully annealed (600 °C), and the normalized/quenched (897 °C) state. Internal Friction (IF) spectra and anelastic modulus parameters were obtained in a vibrating reed apparatus between the temperatures of 100 K and 500°K (–173 °C and 227 °C) at a resonant mode frequency of 103 Hz. The thermal treatments resulted in distinct microstructural evolution, ranging from the low-defect, high-crystallinity state of the annealed samples to a highly defective structure characterized by nanograins and deformation twins in the quenched material. Crucially, the normalizing/quenched sample exhibited the highest amplitude IF peaks (e.g., 350°K). These prominent peaks are attributed to energy dissipation at high-energy grain boundaries and complex dislocation-point defect interactions. Microstructural findings were obtained using transmission electron microscopy (TEM), which identified the presence of dislocations and nanograins. Hasiguti and Bordoni peaks were identified in the IF spectra. The findings establish a methodology for engineers to tailor the dynamic damping capacity and stiffness of CP-Ti for applications requiring stable performance under dynamic loads and cryogenic environments.