Thermodynamic modeling of Cr and Cr–H systems up to high temperatures and high pressures

International audienceA complete literature review of the thermodynamic and phase diagram properties of pure Cr and Cr–H system has been carried out. A thermodynamic assessment using the Calphad method has been accomplished up to 50 GPa for Cr including the liquid phase and up to 18 GPa on the Cr–H system using the most relevant literature data and our own ab-initio calculations. An up-to-date phase diagram of the Cr–H system is presented. Special attention was paid to the fcc phase to clarify the structure type (NaCl, hydrogen atoms located in the octahedral site of the fcc structure) and the composition (one hydrogen per chromium atom). The robustness of our proposed Cr and Cr–H models was demonstrated by comparing our measurements of pressure-composition isotherms of a bcc Cr–Zr alloy with the prediction made by combining the thermodynamic descriptions of the three Cr–H, H–Zr and Cr–Zr binary systems