Dilatometric Analysis of Phase Fraction during Austenite Decomposition into Banded Microstructure in Low-Carbon Steel

Abstract

The evolution of microstructural bands in low-carbon steel gives rise to the orientation dependence of dilatation behavior, which is associated with a distinct, specimen-orientation-dependent, nonisotropic dilatation. In this article, the authors attempt to analyze the phase fraction from the dilatometric curve, which shows orientation dependence due to the effect of microstructural directionality. The contribution of nonisotropic dilatation to the observed dilatation behavior is quantified and integrated into the analysis procedure by considering its evolution from the microstructural and the geometric effects. The proposed dilatometric analysis is applied to the evaluation of the phase fraction during austenite decomposition into a banded microstructure in a low-carbon steel. From dissimilar dilatometric curves measured along different specimen orientations, the phase fractions involved with the austenite decomposition can be consistently evaluated with the proposed analysis procedure. The analysis results are also in agreement with the metallographically analyzed ones.