Striation and faceting of grain boundaries in nickel due to sulfur and other elements

As is the case for free surfaces, the grain boundaries of metals may show striation and faceting as a result of the effect of certain elements. This is true for nickel containing sulfur, tellurium and bismuth, and for copper containing bismuth. In all of the cases, the phenomenon occurs only when the grain boundary concentration of the element concerned approaches saturation, and material transport is taking place towards or away from the grain boundaries. Thus, intergranular striation and faceting are telltale signs of a non-equilibrium segregation. Formerly Research Associate, Département de Métallurgie, Ecole Nationale Supérieure des Mines de Saint-Etienne Formerly Professor, Département de Métallurgie, Ecole Nationale Supérieure des Mines de Saint-Etienne.