Shock melting of tin

An accurate understanding of the Sn phase diagram is needed to correctly interpret experiments examining ejecta, cavitation, and multiphase strength. A recently published multiphase equation of state (Rehn et al.) has suggested that δ-Sn (bcc) should form prior to incipient melt along the principal Hugoniot, with the two-phase region extending from nominally 57-73 GPa. This two-phase region lies at significantly higher pressures than previously anticipated based on previously reported shock release experiments. In this work, X-ray diffraction (XRD) was used to examine the phase evolution along the Sn Hugoniot from 30-85 GPa. The results of these experiments are presented and discussed in the context of the Sn phase diagram with an emphasis on the extent of the solid-liquid two-phase region and whether Sn melts from the δ phase along the principal Hugoniot.