The thermodynamic analysis of GP zones in aged–supersaturated Al–Ag alloys

As the structural cause of hardening, Guinier–Preston (GP) zones in many alloys continue to attract great interest. The energy expressions for GP zones in the Al–Ag binary system, including the εε-state and the ηη-state ones, are established by combining the essential Gibbs energy for the matrix alloy with the interfacial energy and the strain energy. On the basis of the equilibria between GP zones and their surrounding matrix, the size, the composition and the precipitation sequence of different static GP zones are analyzed quantitatively at the defined matrix compositions and the aging temperatures. The calculated results can be used to explain the experimental results well.