Comparison of Ab-initio Solute-Boundary Binding Energies and Experimental Recrystallization Data in Austenite for Solute Nb and Other Elements

Abstract

Niobium is a critical alloying element in modern steels, which is usually employed at microalloy concentrations in the hundredths of mass percent. Since its incorporation into industrial steels in 1958, Nb has enabled the development of the important class of high strength low alloy steels through its ability to limit prior austenite grain size and recrystallization. One of the mechanisms by which Nb is believed to limit grain growth is through solute drag on austenite grain boundaries. This study presents the first direct calculations of the binding energy for solute Nb at austenite grain boundaries, along with binding energies for additional important alloying elements in steel for which experimental data are available. The binding energies are then compared to select data sets for austenite recrystallization from the literature. The strong correlation between the calculated energies and the experimentally measured effects of the alloying elements confirms that the origin of the significant solute drag effect of Nb is the strong binding energy between solute Nb and austenite grain boundaries.