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

Abstract

669.35:536.717 Thermodynamic properties of alloys and phase diagram of Cu − Mn system have been assessed in the spirit of the CALPHAD-approach using simultaneously data about thermodynamic properties of phases and their equilibria. Thermodynamic data are known only for liquid and (Cu, γMn)-phase, model parameters for (δMn)-and (βMn)-phases were therefore estimated using phase equilibria data. The excess Gibbs free energy of phases is described by models with Redlich-Kister polynomials. The models of Gibbs free energy of liquid and (Cu, γMn)-phase take into account excess heat capacity of these phases. Thermodynamic model of the system provides a self-consistent description of all thermodynamic values and phase equilibria, including metastable immiscibility of (Cu, γMn)-phase in close agreement with experimental data. Low-temperature part of the diagram is added in accordance with published data on ordering reactions in (Cu, γMn)-phase.Interaction of copper and manganese remains an object of intent attention of researchers for more than one hundred years. Initially the interest was caused by the favorable combination of mechanical and technological properties of binary alloys of the system and multicomponent compositions based on them. In addition to a good workability, manganese bronzes exhibit high-temperature strength and corrosion resistance [1]. Manganese is an effective modifying addition to cast brass, favorably affecting their technological properties [2] at the same time. To particular physical properties of the copper − manganese system it is possible to refer their high electrical resistivity [3], which not really depends on temperature, and a wide spectrum of magnetic transformations including paramagnetism, antiferromagnetism, and transition into the state of spin glasses [3,4]. Subsequently it was established [5, 6] that alloys rich in manganese have typical combination of high strength and plasticity with very high damping capacity. These alloys effectively absorb the energy of mechanical vibration and thus may be used as construction materials in order to prevent noise and vibration [7]. The alloys rich in manganese demonstrate a reversible shape memory effect [8] that makes them promising for use as an activator material in micromachines [9].The copper − manganese system is one of the few systems in which two transition metals differing markedly in properties demonstrate total mutual solubility. Resulting solid solution shows a tendency towards ordering in the range of copper rich alloys, and a tendency towards metastable immiscibility in the range of manganese rich alloys. All of it makes copper − manganese system an notheworthy object for study by both modern material science and fundamental investigations. PHASE EQUILIBRIAStable transformations. A review of work devoted to studying the phase equilibria in the system carried out before 1939 is given in [10][11][12]. By the opinion of authors [10] most part of obtained results contain errors connected with the fact that manganese used in expe...

Phase equilibria and thermodynamics of binary copper systems with 3d-metals. VII. Concentration-temperature dependences of the thermodynamic functions of mixing for liquid alloys of copper and transition metals

“…Isotherms of integral enthalpy of mixing copper with transition metals (kJ/mole) obtained experimentally at different temperatures shown in [1,8,[40][41][42][43][44][45] that for the purpose of phenomenological modeling of systems with negative deviations of the excess thermodynamic properties from the ideal behavior, it is possible to employ the ideal associated solution (IAS) model. Mathematical models were used in [2][3][4][5] to describe the temperature dependence of the thermodynamic functions of mixing for melts with positive deviations from the ideal behavior. This section generalizes the data on the temperature dependence of the thermodynamic properties of binary systems: copper with 3d-metals and copper with transition metals of the fifth period, Y, Zr, and of the sixth period, La, Hf, Au.…”

“…They The excess heat capacity of Cu-Mn melts is sign-variable: it low and negative for the copperrich melts and is positive in the remaining concentration range. This concentration dependence of the function can be described using two coefficients C 0 and C 1 [4]. Figure 4 presents the temperature-concentration dependences of the mixing enthalpy, excess free energy of mixing, and thermodynamic activity of copper over the entire range of compositions and a wide range of temperatures.…”