A study of thermodynamic properties and association in the Al-Cu melt and their relation to quasicrystal formation conditions

Thermodynamic and Structural Study of the Copper-Aluminum System by the Electrochemical Method Using a Copper-Selective Beta″ Alumina Membrane

“…The copper activity agreement is found to be acceptable at the single previously-studied temperature of 1373 K, falling within the range of literature values [9][10][11][12] for all compositions studied except for 40 mol%, for which the electrochemical data underestimated the activity by 45%. Aluminium activity predicted from electrochemical data using Eqn(8) systematically underestimated the literature values [9][10][11] by 15, 25, and 50% at compositions of 20, 40, and 60 mol% Cu respectively, arising from numerical error in fitting the data for the Gibbs-Duhem integration (Eqn 5). Study of additional compositions would support greater accuracy for the Gibbs-Duhem numerical integration, though clear trends can already be noticed.…”

“…EMF data were fitted linearly in this temperature range, using Eqn(7) to determine partial molar enthalpy and entropy. The corresponding activities of copper and aluminum at 1373 K (1100 °C) calculated using Eqn(6) are presented in Figure 8, and compared to literature values obtained by other methods [9][10][11][12] . The copper activity agreement is found to be acceptable at the single previously-studied temperature of 1373 K, falling within the range of literature values [9][10][11][12] for all compositions studied except for 40 mol%, for which the electrochemical data underestimated the activity by 45%.…”

“…The corresponding activities of copper and aluminum at 1373 K (1100 °C) calculated using Eqn(6) are presented in Figure 8, and compared to literature values obtained by other methods [9][10][11][12] . The copper activity agreement is found to be acceptable at the single previously-studied temperature of 1373 K, falling within the range of literature values [9][10][11][12] for all compositions studied except for 40 mol%, for which the electrochemical data underestimated the activity by 45%. Aluminium activity predicted from electrochemical data using Eqn(8) systematically underestimated the literature values [9][10][11] by 15, 25, and 50% at compositions of 20, 40, and 60 mol% Cu respectively, arising from numerical error in fitting the data for the Gibbs-Duhem integration (Eqn 5).…”

“…[60] A table summarizing all thermodynamic data is included in Appendix 2. Previously reported peak experimental values for enthalpy of mixing range from -4.5 kJ/mol [61] to -18 kJ/mol [9,11,12] . Our peak enthalpy of mixing is in close agreement with that presented [44] by Kubaschewski and Alcock.…”

“…Examples of the corresponding processing issues include macrosegregation [5] or control of the copper content when using recycled feeds [6,7] . Indeed, despite the prevalence of copper-aluminium alloys in industrial applications, liquid phase phenomena remain uncertain starting from inconsistencies in models for copperaluminium thermodynamics [8][9][10][11][12][13][14] and melt structure [15][16][17][18] . In addition, while physical properties such as density, viscosity, and surface tension of copper-aluminium melts have received experimental attention [13,[19][20][21][22] , such quantities are difficult to measure accurately for molten aluminium alloys [19] and limited effort is found to relate these properties to accurate experimental thermodynamics of mixing data.…”