Kinetics of the isothermal precipitation of graphite in white cast irons

The data indicate that up to about 40% transformation, growth is controlled by diffusion rate of Fe and Si atoms away from graphite particles. Subsequently, growth is controlled by the rate of solution of cementite. The latter mechanism is a first- order reaction over the transformation range for which it is in control. The enhanced transformation rate obtained with increase in Si content is attributed to the pronounced effect of silicon on nucleation rate as opposed to its influence on growth- controlling process.