It was recalled that strengthening by small coherent body-centered cubic precipitates of Cu was an important factor in the in-service irradiation hardening of ferritic pressure-vessel steels. The dislocation effects which were involved were studied here by means of atomic-scale computer simulation. Many-body interatomic potentials for the Fe¯Cu system were used to investigate stacking-fault energy surfaces and to simulate the atomic structure of the <111> screw dislocation in both pure α-Fe and in the metastable body-centered cubic phase of Cu. In Fe, the core exhibited the well-known 3-fold form of atomic disregistry. However, in body-centered cubic Cu the core became delocalized by transformation of the Cu as the lattice parameter was reduced in order to mimic the strain

 which was experienced by precipitates. Simulation of a screw dislocation threading through the center of a body-centered cubic Cu precipitate, in an α-Fe matrix, showed that the extent of core delocalization depended upon the precipitate size. The dislocation energy changes indicated the existence of an appreciable dislocation pinning effect, due to this dislocation-induced precipitate transformation process.

Computer Simulation of the Core Structure of the <111> Screw Dislocation in α-Iron Containing Copper Precipitates - I. Structure in the Matrix and a Precipitate. T.Harry, D.J.Bacon: Acta Materialia, 2002, 50[1], 195-208