Abstract
The ability to understand and predict the response of matter at extreme conditions requires knowledge of a material’s equation-of-state including the location of phase boundaries, transition kinetics, and the evolution of material strength. Cerium is a material with a complex phase diagram that continues to attract significant scientific interest. Recent dynamic experiments have provided information on the low-pressure γ–α phase transition, sound speed, and Hugoniot data for the higher-pressure α phase, as well as the incipient shock melt transition. Despite these efforts, there are still regions of the phase diagram that are largely unexplored dynamically, including the high-pressure region below the melt boundary. Along a room temperature isotherm, diamond anvil cell data report a transition to the ϵ phase between 13 and 17 GPa. At higher temperatures, similar diamond anvil cell data show significant disagreement regarding the existence, location, and slope of the ϵ-phase boundary. In this work, double-shock loading was used to access the α–ϵ region of the phase diagram to obtain equation-of-state information and to determine the location of the ϵ-phase boundary for shock loading.
Highlights
Dynamic experiments have been used for decades to examine the response of materials at extreme conditions to study phenomena including phase transitions,[1,2] elastic–plastic deformation,[3,4,5] and material strength.[4,6] Because traditional shock wave measurements access states along the principal Hugoniot, more complex loading methods are required to access other regions of the phase diagram off of the principal Hugoniot to locate phase boundaries, to obtain equation-of-state (EOS) data in each phase, and to examine the evolution of more complex phenomena including damage and material strength
Along a room temperature isotherm, diamond anvil cell data report a transition to the ε phase between 13 and 17 GPa
Along a room temperature isotherm, cerium undergoes a 13%–16% volume collapse as it transforms from the γ phase to the α phase followed by the emergence of the ε-phase between 13 and 17 GPa,[8,28] which exists to pressures in excess of 100 GPa.[29]
Summary
Dynamic experiments have been used for decades to examine the response of materials at extreme conditions to study phenomena including phase transitions,[1,2] elastic–plastic deformation,[3,4,5] and material strength.[4,6] Because traditional shock wave measurements access states along the principal Hugoniot, more complex loading methods are required (e.g., ramp compression, multiple shock loading, and pre-heating methods) to access other regions of the phase diagram off of the principal Hugoniot to locate phase boundaries, to obtain equation-of-state (EOS) data in each phase, and to examine the evolution of more complex phenomena including damage and material strength. Cerium metal is an exciting and ideal choice for studies focused on dynamic material properties because of its complex phase diagram coupled with the large body of diamond anvil cell data[7–17] and shock wave data[18–22] available. Along an elevated temperature isotherm (.600 K) above the solid–solid critical point, a direct α to ε transition has been reported, there are disagreements in both slope and location of the boundary.[30–32]
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