EFFECT OF BORON, CARBON, PHOSPHORUS AND SULFUR ON INTERGRANULAR COHESION IN IRON

Spin-polarized LMTO calculations were performed on a simplified model of a (111) Σ3 tilt grain boundary (GB) in bcc Fe. The GB was modelled by a hexagonal 8-atom supercell containing an impurity atom (B, C, P or S) in the center of a capped trigonal prism of Fe atoms at the GB core. It was found that the bonding of atoms in the GB plane is enhanced due to strong hybridization between electrons of Fe and the impurity. Across the GB the bonding is rather strong for B and C, while it is dramatically weakened for P and S, with d-electrons of Fe occupying almost entirely nonbonding states. The magnetic moments of Fe atoms in the GB were found to decrease with respect to those in the bulk, while the magnetic moments of Fe atom pairs across the GB were enhanced. Our results should be important for understanding the GB embrittlement in Fe and Fe-base systems. © 1990.