Pinning Effects on Grain Growth of Ferrite in an Fe–C–B Alloy

Abstract

The pinning effects of second phase particles on the grain growth of ferrite were studied in an Fe–0.1C alloy containing 5 ppm boron (B). The number and size distribution of Fe3(CB) particles were measured at grain faces, edges and corners by serial sectioning. The particle size was determined from the number of consecutive sections on which the particle was observed. The proportion of particles at each grain boundary site was significantly greater than that of random distribution. The modified Zener theory which assumes that all grain boundaries are pinned by particles could explain the grain size very well, whereas the theory which considers that the pinning of grain boundary corners plays a major role gave a smaller grain size than experiment. Nishizawa et al.'s correlation model accounted well for the number of pinning particles on grain boundaries as well as the grain size. The Hunderi–Ryum's model which takes into accounts pinning of all grain boundary sites gave results close to experiment when a larger proportion of pinning particles at boundary sites than random distribution was incorporated.