THERMODYNAMICS OF STABLE AND METASTABLE PHASES IN THE Ni-Zr AND THE Co-Zr SYSTEM AND THEIR APPLICATION TO AMORPHOUS PHASE FORMATION

Abstract
The thermodynamic functions of the phases in the Ni-Zr and the Co-Zr system are calculated from the experimental data by applying the CALPHAD method. In the case of the undercooled liquid its excess specific heat is taken into account resulting of a pronounced stabilization of the liquid state at lower temperatures. Below T_g the amorphous phase is considered which exhibits a free energy comparable to the one of the intermetallic compounds. From the calculated free energy functions the concentration ranges of amorphous phase formation can be determined and compared to the experiments. Results obtained by mechanical alloying and ion-mixing of the components will be discussed with respect to the assumption of a metastable equilibrium between the phases involved, whereas T_o lines of the terminal solid solutions are used for the interpretation of amorphous phase formation by melt-spinning.