The comparative effectiveness of Nb solute and NbC precipitates at impeding grain-boundary motion in Nb steels

The comparative effectiveness of solute Nb and NbC particles at impeding grain-boundary motion is treated theoretically. It is shown that, for a steel containing ∼0.05at.% Nb (∼0.1wt.% Nb), under typical recrystallization conditions, solute Nb is more effective in the ferrite, whereas in the austenite, depending on the exact recrystallization temperature, either solute Nb or NbC precipitates may be more effective.