A New Type of Microstructural Instability in Superalloys - SRZ

Abstract

A new type of instability in superalloys has been observed in advanced alloys containing high levels of refractory elements. One instability occurs under the diffusion zone of coatings and has been called secondary reaction zone or SRZ. Similar instabilities, in the form of cellular colonies, have been observed along grain boundaries and in dendrite cores. These microstructural instabilities are characterized and interpreted in terms of a nucleation and growth transformation.