Morgan-Mercer-Flodin (MMF) and Johnson-Mehl-Avrami (JMA) are growing models used in the description of kinetic processes in the solid state. In this work, the parameters behavior of these models was compared, in two parametrizations, when fitted to experimental data of isothermic microhardness changes with the aging time, in the Cu-3wt.%Al-5wt.%Ag alloy, at five different temperatures. The data were fitted by the usual linearization of the model function and by a more refined non-linear regression fit. The frequencies distribution of the parameters estimates were obtained by simulation, together with the relative errors. The results indicate that, for one of the model functions parametrization, the kinetics parameter estimates showed a greater stability. Although these functions were considered as distinct functions, it was possible to observe that the MMF function is an approximation of the JMA function and the latter, with the right parametrization, is more convenient to describe the kinetic process here considered.
Nonlinear regression; parameter estimation; simulation; precipitation kinetics; copper-based alloys
