Ti-6Al-4V to over 1.2 Terapascals: Shock Hugoniot and off-Hugoniot Release Experiments, Ab-initio Calculations and a Broad-Range Multiphase EOS.

The most used titanium alloy, Ti-6Al-4V (Ti64), has excellent mechanical and biocompatibility properties with applications in aerospace, defense, biomedical and more. We extend the principal shock Hugoniot for Ti64 to more than threefold compression, up to over 1.2 TPa with high-fidelity experimental shock compression data measured on Sandia's Z machine. A highly reliable multiphase Equation of State (EOS) for Ti64 is developed, spanning a broad range of temperature and pressures. Shock release data are also presented, which provide additional constraints on the EOS model, in an off-Hugoniot regime, where experimental data have not yet been reported. The high-precision experimental results and high-fidelity simulations demonstrate that the Hugoniot of the Ti64 alloy is stiffer than that of pure Ti and reveal that Ti64 melts on the Hugoniot at a significantly lower pressure and temperature than previously modelled.