ABSTRACT
The chemical compositions of grain boundaries in a material are often very different from that of the matrix surrounding them. Although major alloying elements can be enriched or depleted at the grain boundary, it is primarily the enrichment of impurity elements at the grain boundary that has given rise to the greatest differences in composition and has also had the most significant effects on properties. For example, elements such as phosphorus, tin, and antimony may have bulk compositions on the order of 0.005–0.06 wt%, but at the grain boundary they may have local concentrations of 5–10%. These segregated impurities can have many effects on the properties of materials, but two of the most common and most detrimental are an increased propensity to intergranular brittle fracture and intergranular environmental failures (corrosion, stress corrosion, and hydro-gen-assisted cracking). It is primarily because of these types of effects that so much attention has been given to understanding how segregation occurs and also to the development of cleaner materials.
