Kinetics and Microstructural Control

· The rate of phase transformation depends upon the formation and growth rate of the stable nuclei which depends on the rate of atom addition.
· The growth rate (dg/dt) goes to zero at T_E because there is no chemical potential gradient driving the diffusion. It also goes to zero as T goes to zero because the Boltzmann probability term for transport goes to zero.

· The phase transformation rate, (dP/dt), shown opposite is the product of the nucleation rate (dN/dt) and the growth rate (dg/dt)

From: Barrrett, Nix & Tetelman, "The Principles of Engineering Materials," Prentice Hall (1973)