Structural studies of Y2O3 dispersoids during mechanical milling and annealing in a Fe-15 Y2O3 model ODS alloy

The Fe-15 wt% Y2O3 model Oxide Disperson Strengthened (ODS) alloy powder was prepared by mechanical milling in an inert atmosphere using high energy planetary ball mill. The present paper deals with the study on structural changes of nano-crystalline yttria dispersoids in Fe matrix during mechanical milling for various durations and subsequent annealing. The crystallinity of Y2O3 in the milled powder was studied by X-ray diffraction (XRD) technique which showed that the intensity of diffraction peaks of Y2O3 gradually disappeared with increase in milling time. Dark field TEM imaging of the milled powder showed that both Fe and Y2O3 particles were refined to few nanometers during milling. Electron diffraction analysis showed polycrystalline rings for Fe and broad rings with a few spots corresponding to the (4 1 1) plane of Y2O3 after 10 h of milling time. The yttria diffraction peaks became broad and diffuse with increasing milling time. Subsequent annealing of the 60 h milled powder at 1273 K for 1 h results in recrystallization of Y2O3 and growth of Fe crystallites.