Hardness based model for determining the kinetics of precipitation

A theoretical model based on Johnson-Mehl-Avrami (JMA) formalism for determining kinetics and activation energy of a precipitation process is derived from the variation in hardness properties. Effectiveness of the model for determining the kinetics of β-NiAl precipitation in PH13-8Mo steel and for distinguishing the kinetics between two temperatures is also demonstrated. The activation energy for β-precipitation, 244.3 kJ/mol, determined over 808 K to 868 K is in good agreement with that of diffusion of Ni and Al in α-iron.