High strain-rate behavior of two Ti-6Al-4V alloys with different microstructures

摘要

High strain-rate behaviors of two Ti-6Al-4V alloys, processed to develop different microstructures, were studied in ballistic impact experiments and in high rate compression tests. Plate stock of the first alloy was rolled to thickness at a temperature above the beta-transus temperature, resulting in an acicular alpha+beta microstructure with the prior beta grain boundaries. The second alloy was rolled below the beta-transus temperature, resulting in a microstructure of primary alpha and acicular alpha+beta. In high-rate split Hopkinson bar (SHB) compression tests, both alloys failed by shear localization. The alloy processed below the beta-transus temperature was more susceptible to an early shear failure in the SHB tests, with a lower average strain-to-failure value than the alloy processed above the beta-transus temperature. Ballistic tests were conducted with 30mm APDS projectiles, fired against the plates at an angle of 60° obliquity. The alloy with higher average failure strain in the SHB tests also proved to be more resistant to shear plugging failures in the ballistic tests, and offered the greater armor protection. These results are consistent with the hypothesis that an armor material's propensity for localized shear failure degrades its performance.