Shock wave experiments on gallium

Gallium exhibits a complex phase diagram with multiple solid phases, an anomalous melt boundary, and a low-temperature melt transition making it a suitable material for shock wave studies focused on multiphase properties including kinetics and strength. Apart from high-pressure shock wave data that exists for the liquid phase, there is a clear lack of data in the low-pressure regime where much of the complexity in the phase diagram exists. In this work, a series of shock wave experiments were performed to begin examining the low-pressure region of the phase diagram. Transmission experiments were performed to examine the shock wave profile after propagation through a 1.5 mm thick sample of gallium. These were followed by front-surface impact experiments to obtain Hugoniot data in the solid phases to search for the low-pressure phase boundary known to exist statically at 1.5 GPa. The data presented were compared with a theoretical Hugoniot obtained from a previously reported multiphase equation-of-state (EOS) developed using static data showing reasonable agreement and pointing to a phase transition in the 1.2 to 1.7 GPa range. Further implications and possible future studies using gallium will be discussed (LA-UR-17-28291).