Shock-induced melting in bismuth

Abstract

Polycrystalline bismuth specimens were impacted in plane‐wave experiments at stresses of 2.3–2.9 GPa (29 kbar) and for initial temperatures ranging from room temperature to 523 °K. These impact stresses are sufficient to produce final states in the solid II phase of bismuth. For initial temperatures below 435 °K, the Hugoniot in the solid I phase of bismuth intersects the solid I‐solid II phase boundary; the dynamic measurements of the solid I‐solid II transition pressure over this temperature range and the quasistatic measurements of the phase boundary are in good agreement. For initial temperatures above 435 °K, the Hugoniot intersects the melt boundary and melting can occur during shock compression. It is found that there are no discontinuities in the wave profiles, as expected from hydrodynamic predictions for instantaneous melting. Instead, the wave profiles are highly dispersive for initial temperatures near melt. Nevertheless, melting is inferred from the present measurements by comparing the stress states attained during the shock compression with the known phase diagram for bismuth. The present data also show that deviatoric stresses are present for initial states within 20 °K of ambient melt.