Phase Fraction Estimation Using Measured Dilation, a Lattice Parameter Model, and a Curve-Fitting Method

Dilatometry is a measurement frequently used to analyze phase transformations in steels during austenite decomposition. Such analyses are essential for the design of heat treatments and for determining the final phase fractions. This paper presents a simple and systematic method to estimate the evolution of the non-measurable phase fraction of ferrite, pearlite, bainite, and martensite during Continuous Cooling Transformation (CCT) experiments. The optimization-based method uses the measured dilation curve, a lattice parameter model, and a semi-empirical curve-fitting method. The latter assumes specific shapes of the transformation rates. The proposed approach can reconstruct the dilation curve and estimate the phase fractions with high accuracy.