Comparison of dendrites of a pure material with thermal alloy dendrites: an experimental method to estimate the T0-temperature Original Research Article

Complete solute trapping during alloy solidification is considered to be a process which takes place under extreme non-equilibrium conditions. To show how thermodynamic considerations are used in the theoretical description of solute trapping, the relation between the temperature at the interface T and the growth velocity V is derived for pure materials and for binary dilute alloys. It is shown that in alloy solidification with complete solute trapping the T−V relation is similar to that of a pure material with a hypothetical “melting point” given as the T0-temperature. Here, T0 is defined as the temperature at which the free energy of liquid and solid, both with the same concentration, is equal and the solid/liquid interface is at rest. From the comparison of bath undercoolings necessary to achieve similar dendritic growth velocities during pure material growth and complete solute trapping growth of dilute alloys, an experimental method to estimate T0 is discussed. The comparison of T0 estimated by this method with the theoretical predictions shows reasonable agreement.