Evaluation of the maximum transformation rate for analyzing solid-state phase transformation kinetics

An evaluation of the maximum in the transformation rate of a solid-state transformation is given for isothermal and isochronal transformations, on the basis of a general, flexible, analytical transformation model incorporating different combinations of nucleation, growth and impingement modes. For isothermal phase transformations, the position of the peak maximum is determined by the growth exponent and the impingement mode whereas, for isochronal phase transformations, only the impingement mode influences the position of the peak maximum. A straightforward method has been developed for determining the mode of impingement and the separate activation energies for nucleation and growth. The results obtained by application of the proposed transformation-rate maximum analysis to model systems are in good agreement with the values assigned to the kinetic parameters of the model systems. The proposed recipes have also been applied successfully to experimental data on the crystallization of an initially amorphous Mg-Cu-Y alloy.