Dilatometric analysis of phase transformations in hypo-eutectoid steels

Dilatometry is a useful technique to obtain experimental data concerning tr ansformation kinetics in ferrous alloys. This technique is commonly used in cooling experiments to study the austenite decomposition of hypo-eutectoid steel grades. In the standard analysis of the dilatation signal there are two factors that are normally neglected. During the pro-eutectoid ferrite f ormation the austenite enriches in carbon, resulting in a non-linear temper ature dependence of the specific austenitic volume. Furthermore, the specif ic volume of the formed ferrite is considerably different from that of the formed pearlite. In total not taking into account these two effects can lea d to an error in the determined fraction ferrite of up to 25%. A method is presented that takes into account the two above-mentioned factors. In order to determine both the fraction ferrite and the fraction pearlite, in the a nalysis the temperature range of the transformation is divided into a ferri te-formation range and a pearlite-formation range. Two possible criteria fo r this division are discussed, and it is shown that the choice does not hav e an essential influence on the results. (C) 2001 Kluwer Academic Publisher s.