Grain boundary segregation and grain growth inhibition in silicon iron: The effect of boron and nitrogen

Abstract

The degree of grain growth inhibition in iron-3.1 pct silicon alloys with small additions of boron, nitrogen and sulfur has been observed to correlate strongly with the degree of nitrogen segregation to the grain boundaries. Grain growth was seen to increase monotonically with decreasing nitrogen segregation at 950°C, the temperature at which significant grain growth was first observed to occur. Boron affected the retention of nitrogen in the material at high temperatures and in this way had an indirect effect on grain growth inhibition. Sulfur acted to enhance the effectiveness of nitrogen as a grain growth inhibitor. It is suggested that nitrogen, even at very low grain boundary concentrations affects grain boundary migration by poisoning sites at the grain boundaries which are particularly efficient in attaching atoms to the growing grain surface.