Thermodynamics Of Materials At A High-temperature Limit

Abstract:

The following statement will be discussed herewith ‘Real solid, liquid and gaseous solutions of any composition (and pure gases) gradually approach the state of an ideal solution (perfect gas) as temperature increases (approaches infinity) at any fixed pressure. All excess thermodynamic properties of real solutions gradually approach zero if the reference states of all the components are selected as pure components in the same state as that of the solution and if the concentrations are expressed in mole fractions’. Initial validation of this statement is demonstrated here for high-temperature alloys. Equations describing the temperature dependence of excess Gibbs energy of mixing in accordance with this statement will ensure that artificial inverted miscibility gaps will not appear in the calculated phase diagrams as they often appear when this statement is not obeyed. Different equations will be discussed from this point of view. The above statement is shown to possess all the properties (both good and bad) of a thermodynamic law: i. general validity, ii. impossibility to prove with a 100 % certainty, iii. simple reasoning behind with close to trivial statement and iv. usefulness in interpreting natural phenomena using computational thermodynamics.

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