Determination of static recrystallization and recovery parameters for steel by fitting model to stress relaxation data

Abstract

A model for static recrystallization by Zurob et al. [1] has been fitted to experimental stress relaxation [2] data obtained on a low-alloyed steel using a Gleeble thermomechanical simulator. The model has been implemented as an algorithm that calculates the stress relaxation as a function of time, including physical descriptions of the recovery and recrystallization processes. The activation energy and volume were used as fitting parameters for recovery, and the activation energy of diffusion and nucleation site density were used as the fitting parameters for recrystallization. The four fitting parameters were determined from the experimental data by applying the Nelder-Mead algorithm within Matlab software. It can be concluded from the preliminary results that Zurob’s model can be successfully fitted to the stress relaxation data in order to illustrate the static restoration characteristics and kinetics in carbon steels using these fitting parameters.

Microstructure evolution and static recrystallization kinetics in hot-deformed austenite of coarse-grained Mo-free and Mo containing low-carbon CrNiMnB ultrahigh-strength steels

“…Table 2 gives some values of Zurob fitting parameters including the activation enthalpy U a , activation volume of recovery V a and the activation energy for the diffusion of alloying elements Q d for the investigated steels. The obtained values also have physical meaning, so they can be used to estimate the quality of the fitted results and are comparable with results reported by other authors [20]. It must be noted that the values can have some error due to the nature of the relaxation test, which often has some noise, as well as the numerical fitting method, where multiple variables are simultaneously fitted.…”

“…The value of surface to volume ratio fitting parameter (S v ) is set as constant value of 80,839.75 m − 1 . So, the product of geometrical factor fitting parameter (K) x surface to volume ratio fitting parameter (S v ), resulting in a comparable result with those obtained by Pohjonen et al [20].…”

“…An alternative method to study the recrystallization is the Zurob model, presented originally in [19] and slightly modified by Pohjonen et al in [20]. Equation details are presented in the mentioned articles, but the basic idea is that the model is physically based and considers the effect of recovery as a dislocation density dissipation mechanism, whereas in the K&P equation recovery is just a hand-fitted line.…”

Numerical Modelling of Thermo-Mechanical Processes in Steels - An Overview and Recent Progress

“…Recrystallization An effort has been made for construction and application of recrystallization models. The results of these studies are described in [20][21]. A physically based static recrystallization (SRX) model was implemented and presented in [21].…”

Analysis of grain size distribution evolution of steel during recrystallization and grain growth

“…In addition, various mean field models simulating the average grain size after recrystallization were investigated. In [4], a physically based static recrystallization model was implemented and fitted successfully into experimental stress relaxation test data. The results are promising, but further studies are required to improve model prediction reliability.…”