Computation of the Diffusional Transformation of Continuously Cooled Austenite for Predicting the Coefficient of Thermal Expansion in the Numerical Analysis of Thermal Stress

Abstract

The coefficient of thermal expansion is calculated as a function of the cooling rate, phase composition and temperature. This depends on a numerical method proposed here for computing the phase composition as a function of time and temperature based on the CCT diagram. An exponential equation is used to describe the instantaneous fraction transformed and the parameters in this equation are taken as functions of the transformation start temperature, which in turn is a function of the cooling rate. In the multiphase region, the coefficient of expansion is considered as consisting of two components: thermal and transformational. They are computed from the previously calculated fractions of the participating phases.