On the solute-defect interaction in the framework of a defactant concept

It will be shown that there is an analogy between surfactants in liquids which stabilize structures with large surface areas such as foams or microemulsions, and certain components in a crystalline solid, which stabilize defects such as grain boundaries and dislocations. These components are then called defactants. In the presence of defactants microstructural changes may occur because some of the defects compete more successfully for segregation of the defactants than others. Thus voids are formed at grain boundaries of Cu – Bi alloys because the formation energy of voids is provided by the interaction energy of Bi-atoms of the newly created surface. Or the beneficial role of rhenium on the high temperature creep of superalloys may be interpreted as a deficiency of defactants stabilizing dislocations and/or vacancies. These examples are discussed in the present work after a general treatment of the role of defactants.