Grain boundary character dependence of phosphorus segregation at ferrite grain boundaries in a high-purity iron-phosphorus binary alloy

Grain boundary segregation of solute elements is known to be strongly influenced by boundary characters. In this study, the equilibrium segregation of phosphorus at ferrite grain boundaries was quantitatively evaluated using three-dimensional atom probe after annealing a high-purity iron-phosphorus binary alloy with a low phosphorus content of 0.011 mass% at 873 K for 86.4 ks. The results of multiple grain boundaries with various characters, as analyzed using electron backscatter diffraction combined with characterization of the grain boundary plane orientation, reveal that the amount of phosphorus segregation increases with the increment in boundary misorientation angle, with especially large scatter existing in the case of high-angle grain boundaries. Further analysis via the decomposition of boundary misorientation into the contributions of tilt and twist angles indicates that the enlargement in tilt component has a relatively larger promoting effect on phosphorus segregation than the twist counterpart.