Vaporization of shock-compressed metals on expansion

The authors experimentally determined the rates of expansion into air of five metals (Al, Mg, Cu, Sn, and Cd) with different bond energies and boiling points. In this series of metals Cd has the lowest bond energy and Al the greatest, 12 times the bond energy of Cd. For three metals (Al, Mg, Cu) they obtained smooth monotonic w(u) curves, which indicated the passage of the unloading curves through states of the condensed metal. For Cd and Sn the break on the w(u) curve revealed "critical" shock pressures above which the expansion process led to partial vaporization of the metal.