Phase transitions of copper, aluminum, and tungsten wires during underwater electrical explosions

Using streak images of underwater electrically exploding copper, aluminum, and tungsten wires (current densities of 107–108 A/cm2 and energy density deposition of 10–50 kJ/g) and generated weak shocks, the onset of each phase transition, its duration, and the time when the wire explosion occurred were determined. The measured discharge current and resistive voltage were used to calculate the energy and energy density deposition. Using the discharge current waveform and the onset of the strong shock wave, the specific action integral was calculated and compared with published data. The thermodynamic parameters during the wire explosion were calculated using one-dimensional magneto-hydrodynamic simulations coupled with equations of state for water, copper, and aluminum. It was shown that the onset times of weak shocks, in general, cannot be related to the melting or the evaporation of the entire wire.