Dissociation and core structure of 〈110〉 screw dislocations in L12ordered alloys I. Core structure in an unstressed crystal

Abstract

The core structure of 〈110〉 screw dislocations in ordered alloys with the L1₂ structure has been studied using computer simulation techniques. Dislocations lying on both {111} arid {100} planes in stress-free crystals were studied using three different interatomic potentials corresponding to different antiphase boundary (ABP) and complex stacking fault (CSF) energies on {111} planes. The superlattice intrinsic stacking fault (SISF) energy on {111} planes was held constant in all calculations. When the APB energy is not too high, the dislocation dissociates on the {111} plane into two ½〈110〉 superpartials separated by APS. The cores of the superpartials are planar and similar to those of dislocations in f.c.c. materials. When the APB energy is high, the dislocation dissociates on {111} into two ⅓〈112〉 superpartials separated by SISF, the cores of which can be highly non-planar. On {100} planes the dislocation always dissociates into two ½〈110〉 superpartials, the cores of which are non-planar, spread on one or two {111} planes.