Rate of Peritectic Reaction in Iron-Carbon System Measured by Solid/Liquid Diffusion Couple Method

Abstract

A model experiment was made for study on the effects of temperature on the reaction rate in isothermal peritectic reaction in iron-carbon system by using a soliid/liquid diffusion couple method. Measurements of the variation in carbon concentration over δ, γ, and liquid phases show a decrease in the carbon concentration from the γ/liquid interface to the δ/γ interface and an equilibrium partition of carbon at both the interfaces. The γ-phase grows into both δ and liquid phases. A regression analysis of the thickness of the γ-phase, x (μm), with the reaction time, t (s), results in the following relations.
x=36.6t^1/2 at 1755 K
x=54.7t^1/2 at 1722 K
x=71.0t^1/2 at 1689 K
These relationships imply that the peritectic reaction follows the parabolic law and that the reaction rate is higher at lower temperatures. It was found that about 90% of the γ-phase formed through the peritectic reaction is the transformation product from the δ-phase and about 10% the solidification product from the liquid phase.