Disorder-order transition in multiprincipal element alloy: A free energy perspective

XS Wang and YJ Wang, PHYSICAL REVIEW MATERIALS, 7, 033606 (2023).

DOI: 10.1103/PhysRevMaterials.7.033606

Although the concept of high entropy has flourished in the development of engineeringly important multi principal elemental crystalline materials, the role of entropy is controversial in driving possible disorder-order transition. Here we provide a thermodynamic perspective on this transition based on absolute free energy calculations of a list of equilibrated CoCrNi configurations extracted from the annealing history. A set of new physical quantities associated with the degree of anharmonicity, chemical short-range order, and Shannon-entropy informed disorder temperatures are proposed to signify the disorder-order transition. The interrelationships between these thermodynamic quantities consistently suggest a disorder-order transition that is supported by experimental observation. The analysis further recognizes the critical role of the anharmonic effect in driving the random solid solution to a chemically short-range ordered phase. The free energy insights help us to understand the formation mechanism of locally ordered structures emerged from the solid solution of ideal mixing.

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