Over the past decade, metallurgists have become extremely aware of the fact that the grain boundaries of an alloy may have very different chemical compositions from that of the bulk. In particular, elements normally considered impurities which have bulk concentrations on the order of several hundred ppm may have local concentrations at the grain boundaries of five to ten atomic percent. The effects of grain boundary segregation on intergranular fracture have been particularly well studied.1-40 We now know that the presence of specific elements at the grain boundary can change the preferred fracture path from transgranular to intergranular. Less work has been done which studies the effect of grain boundary segregation on intergranular corrosion. However, many results suggest that segregation affects this process as well.41-49
One concept that has arisen from the studies of intergranular fracture is that the potency of a segregated embrittling element depends on the...
