In order to develop Co-based oxide dispersion strengthened (ODS) superalloys with excellent mechanical properties and oxidation resistance at the temperature above 1000 °C, Co-20Cr-(5,10)Al ODS superalloys were designed and fabricated by mechanical alloying (MA), spark plasma sintering (SPS), hot rolling and the final annealing at 1200 °C. Two different phases were identified; the Co solid solution of a fcc structure, and the B2 phase highly enriched with Aluminum. Composition and volume fraction of both phases are almost consistent with the Co-Cr-Al ternary phase diagram computed with the Pandat software. Another coarse fcc phase with smaller content of oxide particles was also characterized. This phase was probably formed through an incipient melting at the initial stage of SPS process. Fine oxides particles are densely distributed inside both, the fcc solid solution and the B2 phase. Grain boundaries and phase boundaries are decorated with the oxide particles, which are beneficial to grains and phases stability at elevated temperature. The observed unique core-shell structure was characterized as Y2Hf7O17 type in a core and Y2Hf2O7 type at a periphery of the oxide particles.
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