Intergranularfailure in steel: the role of grain-boundary composition

The circumstances under which steels exhibit intergranular fracture can be classified into four general categories: (1) owing to the presence of certain secondary phases at the grain boundaries; (2) owing to thermal treatments which cause impurity segregation to the grain boundaries without the precipitation of an observable second phase; (3) owing to the action of certain environments; and (4) owing to a combination of stress and high temperatures. In this paper each of these categories and their effects on material properties are reviewed. How the chemical composition of the grain boundary influences and induces intergranular cracking is discussed in detail for all four cases.