Thermo-mechanical characterization and dynamic failure of near α and near β titanium alloys

This paper investigates the thermo-mechanical response and failure behaviour of near β Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) and near α Ti3Al2.5 V alloy under high strain rate loading. A series of dynamic compression and shear compression tests have been performed, using a high-speed infrared detector synchronized with a Kolsky bar (split Hopkinson pressure bar). The results show that Ti-55511 presents a higher flow stress with little strain hardening, as opposed to Ti3Al2.5 V. The measured temperature rise preceding the onset of load drop is modest and insufficient to trigger thermal instabilities. Near α Ti3Al2.5 V is characterized by a higher Taylor-Quinney coefficient-βint, which is close to ~0.6 compared to ~0.35 for near β Ti-55511. Microstructural examination reveals that both alloys fail by dynamic shear localization.