The dynamics of clusters during phase transformation can be described by the Fokker-Planck equation. In this paper asympototic behaviours of the Fokker-Planck equation were investigated. The driving force for nucleation in an infinite system is time dependent and the nucleation rate approaches a constant value, steady state nucleation rate. However, if the drivig force is constant during the phase transformation, the number of clusters having the critical size increases with time. Therefore, the number of the stable clusters increases with time in the case that an external driving force is applied to compensate the decrease in the chemical driving force. This result may be helpful to develop a new method of thermomechanical control process.
