This interaction is produced only in superlattices (ordered alloys), not in conven­tional disordered alloys. In a superlattice, there is a long-range periodic arrange­ment of dissimilar atoms, such as in Cu3Au. The movement of dislocations through a superlattice causes regions of disorder called antiphase boundary (APB).

The dislocation dissociates into two ordinary dislocations separated by an APB. As the slip proceeds, more APBs are created. Ordered alloys with a fine domain size are stronger than the disordered state.

2.4.1.2 Stacking Fault Interactions

Stacking fault interactions are important as the solute atoms preferentially segre­gate to the stacking faults (contained in extended dislocation). This effect is also known as Suzuki effect or chemical interaction. The stacking fault energy gets reduced due to the increasing concentration of solutes in the SF, and thus the sepa­ration between the partial dislocations increases making it increasingly harder for the partial dislocations to move.