Dynamic compression of cerium in the low-pressure γ − α region of the phase diagram

Plate impact experiments were performed to examine the dynamic response of cerium for loading paths that span the well known γ−α phase transition. The anomalous nature of the γ-phase and the large volume collapse at the γ−α boundary resulted in a ramp-wave followed by a shock jump for shock loading. This structured wave provided a convenient means for locating the phase boundary and determining the volume collapse at the transition. Experiments using a preheat capability were performed to obtain equation-of-state data, to locate and determine the volume compression along the phase boundary, and to determine the location of the critical point. Experimental results show that the ramp-wave peak increased with the initial sample temperature consistent with an increase in the transition stress while the magnitude of the shock jump decreased. The data were analyzed to determine the volume compression along the boundary pointing to a critical point at 1.648 ± 0.075 GPa. Additional experiments using a shock-release configuration were used to obtain data during release. All data were in good agreement with calculations from a multiphase equation-of-state that treats the γ and α phases as a binary alloy.