Formation of austenite in steels during heating: analysis of dilatation data

A novel method has been presented to estimate the volume fraction of the phases along with their linear thermal expansion coefficients and carbon concentration of austenite directly from the experimental dilatation data of a low alloy (LA) steel. The unusual expansion associated with austenite formation in the LA steel has been investigated. It has been shown that the relative contribution of (i) the variation of the amount and composition of phases with temperatures and (ii) thermal expansion coefficient of the phases have significant effect on the dilatation behaviour. It is also shown that the present method, rather than the 'lever rule' approach, is more appropriate for estimating the amount of austenite from the dilatation curve when it shows unusual expansion.