Dilatometry and calorimetry are well-established techniques, and have been used successfully for decades; however, they are seldom used to quantify the progress of a transformation. Most often, these techniques are used to detect start and finish of transformations. When used quantitatively, current analysis of dilatation data does not account for the different changes in density for the multiple transformed phases. Similarly, quantitative calorimetric analysis does not account for different rates of enthalpy release for different transformed phases. The technique proposed for both dilatometry and calorimetry consists on posing a differential equation based on dilatation or temperature data generated under controlled experimental conditions. When integrated, this equation extracts phase fraction evolution from the experimental data. Like all differential equations, the equation posed involves coefficients and integration constants. The work presented differs from other similar work in that the coefficients are obtained from calibration before, after, and at transition points for each transformation, with a minimum of need of previously tabulated data. The mathematical treatment will be introduced, and applications will be discussed involving solid-state precipitation in Al-Ag, precipitation during solidification in A356, martensitic transformation in creep-resistant steel, and bainitic and martensitic transformation in 4140 steel.

Keywords