Role of strain heterogeneity on recrystallisation of oxide dispersion strengthened Fe–Cr–Al alloys for high-temperature applications

Mechanically alloyed iron-based oxide dispersion-strengthened alloys have the potential for application in heat exchangers for biomass power plants, with operating temperature and pressure at entry of the gas turbine working fluid being around 1,100 °C and 15–30 bar, respectively. 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 study, focusing specifically on PM 2000. The results can be interpreted if it is assumed that anything which makes the microstructure heterogeneous stimulates recrystallization. The combination of these results with finite element modelling is used to interpret the role of strain heterogeneity on the development of recrystallized grain structure. In this sense, larger strain gradients lead to more refined and more isotropic grain structures.