The evolution of Y distribution during the processing route of mechanically alloyed iron studied by means of atom probe tomography

Oxide dispersion strengthening of steels has become quite popular during the last few years. Especially because of their thermal stability, Y-O clusters can improve high temperature properties such as strength, hardness and creep strength. Oxide dispersion strengthened steel is a promising candidate for applications mainly in fast breeder reactors. In order to establish a better understanding of the strengthening mechanism, this study focuses on an evolution of the Y distribution in mechanically alloyed iron during the process route, employing atom probe tomography. After mechanical alloying, Y seems to be distributed in extremely fine clusters and partly dissolved in the matrix. Enrichment of alloying elements in the Y-O clusters in the mechanically alloyed state is evidence for diffusion processes taking place during mechanical alloying. During hot isostatic pressing at elevated temperatures, dissolved Y atoms accumulate and build distinct clusters. These clusters stay stable even after annealing at 600 degrees C for 8 hours.