Effect of Solute Nb on Grain Growth in Fe-30 Pct Mn Steel

Niobium is known to segregate strongly to grain boundaries in steel. The strong interaction of Nb with grain boundaries results in an important reduction of the grain boundary mobility and strong retardation of recrystallization and grain growth. In this study, the effect of Nb on the mobility of grain boundaries in a second-generation Fe-30 pct Mn TWIP steel is investigated. Grain growth kinetics was measured in a series of Nb-containing Fe-30 pct Mn model alloys. An estimate of the grain boundary mobility was obtained for various temperatures and niobium contents. It was found that Nb slows down the mobility of random high-angle grain boundary segments that are not twin related. The effect of solute Nb on grain growth, in the presence of annealing twins, was modeled using Cahn’s theory of solute drag coupled with a recently formulated twin-inhibited grain growth model. The results are shown to be in very good agreement with the experimentally determined growth kinetics.