Unit cell dilation technique for analyzing dilatometry data in microalloyed steels

Dilatometry is the most accurate and common method for measuring the kinetics of phase transformations in solid specimens. Despite the development of a more accurate technique, an inferior method, i.e., the lever rule, is widely used in the scientific community to interpret raw dilatometry data. This paper introduces a sound mathematical approach to modeling the physical phenomena of phase transformations, named continuous sequential phase transformation (CSPT). CSPT is used in creating an algorithm called unit cell dilation (UCD) that is used for analyzing the continuous phase transformation of two microalloyed steels. Results show that the UCD algorithm generates quantitative data for the phase content of the steel that is in good agreement with metallographic observations. The source code for an implementation of the UCD algorithm is distributed under GPL-3.0 license and available for download at (https://github.com/Nassehk/Dilatometry-analysis.git). Comparison of calculations made using the UCD algorithm with quantitative metallography measurements for steel X80-N. UCD stands for unit cell dilation technique and LR stands for lever rule method. [Display omitted] •Lever rule is not an adequate method to analyze dilatometry data.•A method called “Unit Cell Dilation” is developed to analyze the dilatometry data.•The new method calculates phase fractions while accounting for chemical changes during diffusive phase transformation.