Recrystallization Process in Fe-Cr-Al Oxide Dispersion-Strengthened Alloy: Microstructural Evolution and Recrystallization Mechanism

Mechanically alloyed iron-base oxide dispersion-strengthened (ODS) alloys are the class of advanced materials for application in heat exchangers tubing in which creep and oxidation resistance are paramount. The yttria dispersion in such alloys improves the high-temperature creep and stress rupture life. The strength is further enhanced by the development of a coarse-grained microstructure during recrystallization. Factors controlling the evolution of this desirable microstructure are explored in this work, focusing specifically on PM 2000. The results presented in terms of orientation imaging, transmission electron microscopy, and scanning electron microscopy indicate that the recrystallization process consists of two different stages. Before the coarse grain takes place, the alloy undergoes an extended recovery process followed by abnormal grain growth. The initial microstructure consisted of subgrains (submicrometer sizes) with a strong 〈110〉∥RD fiber texture (α fiber), which are transformed into coarse grains (mm sizes) with orientations 〈112〉∥RD. The aim of this study is to describe the mechanisms involved in the intermediate stages of recrystallization process from the submicrometer grain size to the abnormal grain size.