Formularization of softening fractions and related kinetics for static recrystallization using inverse analysis of double compression test

An inverse analysis for obtaining a flow curve equation, which accounts for inhomogeneous strain and temperature distributions, is applied to the evaluation of the softening fraction in a double compression test. To obtain the set of equations in the first and second hits, two approaches are used. One is to determine different sets of coefficients for the first and second hits, independently. The other approach is to introduce the residual strain ɛR in the inverse analysis and to use the same set of coefficients in the first and second hits. Assuming both the rule of additivity for metallurgical strain and static recrystallization kinetics, which depends on temperature and applied strain, the residual strain after dwelling can be related to the recrystallized fraction. Under the above conditions, the effects of inhomogeneous strain and temperature distributions on softening behavior during the double compression test can be investigated. The distribution of softening behavior within a workpiece in plain carbon steel is investigated. The calculated softening fractions are compared with metallographically observed recrystallized fractions at three different observation points. Metallographically observed recrystallized volume fractions agree well with the calculated softening fractions, which accounts for inhomogeneous distributions of deformation and temperature, at higher fractions.