Thermodynamic study of liquid manganese-copper alloys

Abstract

Using a high-temperature torsion-effusion technique, vapour pressures of manganese have been measured over liquid manganese-copper alloys containing 5-100 atom % Mn and at temperatures between 1280 and 1600°K. These have been used to calculate the partial and integral thermodynamic properties of the liquid alloys. Activities and free energies show strong positive deviations from ideality in Mn-rich regions, but negative in Cu-rich alloys ; a rapid variation of Mn activities being observed at approximately 18 atom % Mn. Integral heats and excess entropies of formation are also asymmetric in form, changing from positive to negative with increasing Mn content. Factors influencing the thermodynamic properties are discussed ; it is suggested that the liquid properties reveal the persistence of factors operative in the solid state and are particularly influenced by the variation of the magnetic interaction between manganese atoms.

Activity Coefficient of Manganese in Copper

“…Therefore, the present work measured for the Mn composition less than 0.2 mass% is believed to be more reliable for infinite dilute solution of Mn in Cu. And the temperature dependence of the present work show similar tendency with that of the data by Spencer and Pratt 2) and Hultgren et al…”

“…Spencer and Pratt 2) and Hultgren et al 3) have reported the activity coefficients of Mn in copper at 1 573 and 1 500 K, respectively; however, the temperature dependence of Mn activity coefficient in Cu in the temperature range of 1 623 to 1 723 K was not reported. Therefore, this study aims to derive an equation which correlates the activity coefficient of Mn in Cu to temperature.…”

Standard Gibbs Free Energy of Formation of MnO-saturated MnO Cr2O3 Solid Solution at 1873K.

“…)-Gas system, using the thermodynamic properties of manganese and chromium in molten copper [9][10][11][12][13][14][15] summarized in Table 1(b), the standard Gibbs free energy change of the Reaction (2) in case of MϭCu, DG°2 ,MϭCu , and DG°f , MnO · Cr 2 O 3 were determined from the experimental results for this system. In case of this system, the dissolved chromium, oxygen and carbon in copper phase are so dilute that the terms of their interaction can be neglected.…”

Phase equilibria and thermodynamics of binary copper systems with 3d-metals. IV. Copper-manganese system

“…Satisfactory agreement should be noted for results obtained in [33] at temperature 1573 K with the data in [32], which demonstrate lower endothermic values over a wide compositions range at temperature of 1386 K. The activities of components of liquid alloys for Cu − Mn system (Fig. 8) were studied by authors in [35][36][37].…”

“…In [35] the manganese activity was studied by the Knudsen effusion method for 18 alloys within the temperature range T = 1278-1596 K and compositions range x Mn = 0.048-0.850. According to data [35] the activity isotherm of manganese at 1517 K is presented in Fig.…”