The effect of boron on the grain boundary energies of gamma-iron

The effects of additions of up to 200 ppm of boron on the grain boundary and surface energies of γ-iron were examined. The ratios of these energies to the twin boundary energy, assumed constant, were obtained from measurements of the equilibrium profiles formed on the surface where it intersects the grain and twin boundaries. The surface energy of pure iron was used to convert these ratios to absolute energy values. Boron additions of up to 50 ppm progressively reduced the grain boundary energy to about 70% of the energy for pure iron. Values of 'grain boundary activity' and 'grain boundary enrichment factor' were calculated and compared with values from other binary systems in the literature. This comparison showed that boron in iron behaves as a normal low solubility solute in its action on the grain boundary energies. (author)