Shock-induced mechanical response and spall fracture behavior of an extra-low interstitial grade Ti-6Al-4V alloy

The mechanical response and spall fracture behavior of an extra-low interstitial (ELI) grade Ti-6Al-4V alloy are systemically investigated during one-dimensional shock loading. The effects of oxygen content on the shock response and dynamic failure characteristic of Ti-6Al-4V are also shown through the comparison of the obtained results with those for commercial Ti-6Al-4V. The measured Hugoniot elastic limit (HEL) of Ti-6Al-4V ELI is lower than that of commercial Ti-6Al-4V. While the fitted shock parameters and the measured Hugoniot in the stress-particle velocity space of Ti-6Al-4V ELI are found to be almost identical to those of commercial Ti-6Al-4V. These results indicate that the oxygen content can significantly affect the HEL of Ti-6Al-4V, but has little or no influence on the shock response of this alloy beyond the HEL. The postshock Ti-6Al-4V ELI does not display shock-induced strengthening during quasistatic and dynamic compression tests. Transmission electron microscopy (TEM) analyses reveal that the lack of high density dislocations or dislocation cells limits the shock-induced strengthening effect, although dislocation multiplication and tangles lead to increased yield strength and strain hardening rate of the reloaded material. Finally, Ti-6Al-4V ELI is demonstrated to spall in a ductile manner, and has similar spall strengths to those of commercial Ti-6Al-4V under different shock loading conditions. The oxygen content exerts no effect on the spall fracture manner of Ti-6Al-4V, although reducing the oxygen content enables this alloy to endure more micro-damages.