The Sigma Phase

The sigma phase, which occurs in transition-metal alloy systems, is of interest in both the technological and the theoretical field of alloy formation. In the former, the sigma phase is important because of its occurrence, with generally deleterious effects, in stainless and other high-alloy steels, while in the latter case a knowledge of the properties of the phase may lead to a greater understanding of the alloying behaviour of the transition metals.