Materials Center Leoben Forschung GmbH
Recrystallization and its related phenomena play an important role in the evolution of the microstructure-property relationship of ferritic steels. The kinetics of static recrystallization are heavily influenced by the mobility of high-angle grain boundaries (HAGBs). Here, several alloying elements as well as impurity elements, such as Cu, Sn and Mo show strong segregation tendencies to HAGBs and impede their movement, which is known as solute drag. A better understanding of this effect is required for innovative steel production processes for $\mathrm{CO_2}$ reduction like the electric arc furnace (EAF) route, where impurity elements enter from steel scrap.
We employ a state-parameter based mean-field model, which describes static recrystallization in terms of nucleation and growth of recrystallized grains, and incorporates the solute drag effect as a function of alloying elements in work-hardened ferritic steels. In conventional recrystallization models, solute drag effects are usually considered as a fitting parameter. We go beyond this approach by computing solute binding energies at a characteristic $\mathrm{\Sigma5}$ HAGB for a wide range of elements by \emph{ab-initio} simulations and consider their temperature and composition dependent influence on mobility via the Cahn model. Additionally, we investigate solute-solute interactions at HAGBs and consider potential site-competition and co-segregation interplays. The prevalent dislocation density is obtained from a flow stress model, that describes dislocation density as a function of cold-rolling ratio and which is parameterised on flow curves of relevant steel grades. With this model framework at hand, we can show good agreement to experimental data.
Abstract
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