Systemically Study Of Au-Cu Alloy System

In this works the Au-Cu alloys have been systematically studied and analyzed under the framework of systematic science of alloys (SSA).Firstly, the atomic states of pure metal Cu with FCC crystal structure at different temperature have been studied by using the one-atom (OA) theory, Debye theory of solid heat capability and Gruneison equation of thermal expansion, the track of atomic states in three state hybridization triangle varying with the temperature has been calculated. It is found that the bonding electrons (covalence electrons and near free electrons) are reduced, the non-bonding electrons increase while the temperature ascends. Based on this result, the potential curve, the elastic properties and thermodynamic functions, such as heat capacities (C_p,C_v), vibrational energy, enthalpy, entropy and Gibbs free energy of metal copper at different temperature are then calculated. The calculated results are in agreement with the thermodynamic database SGTE at low temperature region, but as temperature gets higher, the discrepancy between them becomes larger. The calculating results below the room temperature can be integrating to the thermodynamic database.According to characteristic crystal theory, the lattice constants, binding energies, atomic states and properties of Au-Cu system have been studied systematically. The atom volume interacting function and energy interacting function between atoms in Au-Cu system with FCC structure are determined. The basic information of characteristic atom sequences and characteristic crystal sequences with FCC structure in Au-Cu system , such as atomic states, potential energy, atom volume and other properties, are obtained. Applying these basic information and the characteristic atom arranging designing technique (CAAD) based on the characteristic crystal theory, the relationship curve of atomic states and properties varying with the alloy concentration of disordered Au_1-xCu_x alloy have been calculated. It is analysed why the lattice constants of Au-Cu alloys show a positive deviation from Vegard's law. The atomic states, heat of formation and other properties of various FCC style intermetallic compounds (Au₃Cu AuCu AuCu₃) with different space groups are studied. The factors stabilizing these stoichiometric intermetallic compounds with same compositions but different space groups are discussed. The subtle structure of crystal cell of AuCu(I) and AuCu(II) with long period structure are studied, the atomic states, potential energies and volume at different sites in crystal cells are calculated. Based on this, the factors which affect the growth of AuCu(I) and AuCu(II) are discussed.The typical ordered phases, such as LI o a LI2, etc., in Au-Cu system have been studied. The relationship curve of lattice constants, potential energies, atomic states, and properties of these ordered phases varying with the concentration and ordering degree of alloy have been calculated. Applying the characteristic atom arranging designing (CAAD) technique, the atomic states, potential energies and volumes of crystal cell and atomic clusters with error arrangement of three typical intermetallic compounds, Llo-AuQu LI2-A113QU LI2-AUCU3, have been studied. The results illustrate that, among the three intermetallic compounds, LI2-AU3CU presents the strongest disordering trend, while LI2-AU3CU has the most stability.Applying statistic thermodynamics based on the characteristic crystal model, the thermodynamic properties of Au-Cu system have been studied. The varying curves of forming heat and activities of liquid alloy and disordered solution are calculated, the calculated results are in good agreement with experimental data. The curves of Gibbs energies, forming enthalpy and entropy of some ordered phases varying with temperature and ordering degree are calculated. The phase diagram of Au-Cu system with liquidus, solidus and ordered phases areas are evaluated. The calculated liquidus and solidus are in agreement with experimental information and other papers, but the evaluated results about ordered phases are in poor agreement with the later.