Transformation of oxide nanoparticles in a nickel-based ODS alloy aged at 1000 C

The transformation of oxide nanoparticles in hot-isostatic-pressing-consolidated nickel-based oxide dispersion strengthened (ODS) alloys during isothermal aging at 1000 degrees C for 200 h has been investigated by means of transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM) herein. By comparing the size, phase and oxide/matrix interface structure of the oxide nanoparticles before and after the aging, the underlying reason for the changes in oxide nanoparticles is analyzed. The results show that Y3Al5O12 nanoparticles are precipitated during the long-term heat treatment, resulting in a change of composition proportion of the oxide nanoparticles. Simultaneously, more Y-Ti-O complex particles are converted into YTiO3 phase. In order to reduce the interfacial energy between particles and matrix, a small number of large and stable particles with core/shell configuration and Janus configuration are formed. It is found that the core/shell structure consists of Y2Ti2O7 as the core and Y3Al5O12 as the shell, while the Janus structure consists of Y2Ti2O7 and Al2O3. Due to the lower lattice misfit between nanoparticles and matrix, and the smaller contribution of grain boundaries and dislocations to particle coarsening, the increase in the average size of oxide nanoparticles in the nickel-based ODS alloy is small.