Microstructure and hardness of nanocrystalline ferritic ODS alloy foil with high oxide content fabricated by EBPVD

Ferritic ODS alloys are attractive due to their high creep and oxidation resistance at temperatures above 1000 °C. However, the effect of yttria content is never discussed, because high yttria content is hardly achieved in the conventional mechanical alloying method. Here we report the fabrication method of ferritic ODS alloy foils with high oxide contents, as high as 8.5 wt.%. The dispersoids in the ODS alloy fabricated by this method are mainly composed of bcc structured yttria, no Y-Al-O nanocluster was detected. The hardness was found to increase with the yttria content linearly, it was taken that both Orowan and Hall-Petch mechanism contributed to the strength.