Calculation of thermodynamic parameters of Mg-Al-Y alloy

Abstract

By means of Miedema formation enthalpy model with Toop model, the excess free-energy, enthalpies of formation, excess entropies and activity values of all components of Mg-Al-Y ternary alloy were calculated with computer programming. The experimental results show that enthalpies of formation, excess free-energy and excess entropies of the ternary alloy are negative in the whole content range, the minimum values at 1 123 K are all obtained at x _Al=55%, x _Y=45%, x _Mg=0%, which are −37.969, −30.961 kJ/mol and −6.24 J/(mol·k) respectively. Activity curves show that the activity values of Al and Y in Mg-Al-Y ternary alloy rapidly decrease with the decrease of molar fraction, the values of which are very small when the molar fraction decreases to 0.4. It means that there is a strong interaction between Al and Y and stable compounds can be form in the Mg-Al-Y ternary alloy system.

Keywords

Mg-Al-Y ternary alloy / thermodynamic parameters / miedema formation enthalpy model / toop model

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