Development of Oxide Dispersed Austenitic Stainless Steel through Mechanical Alloying and Spark Plasma Sintering

The yttria was dispersed in 316L austenitic stainless steel powders processed by mechanical alloying (MA), and subsequently, the oxide dispersed strengthened (ODS) alloy powders were sintered by spark plasma sintering (SPS). Phase and microstructural evolutions were examined by x-ray diffraction, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The 25 h milled sample with 2 wt.% yttria showed the formation of a single-phase FCC structure. The SPSed alloys showed the re-precipitation of yttria from the austenitic matrix. Relative density of more than 95% was achieved in SPSed samples containing 0.5, 1.5, and 2 wt.% yttria dispersion. The dispersion of yttria has shown a profound effect on the mechanical properties by restricting the grain growth kinetics in the sintered samples. The SPSed sample of 2 wt.% yttria has shown a high value of microhardness of similar to 6.9 GPa, which can be attributed to the dispersion of nano-yttria in the austenitic matrix. The impression creep results showed the primary and steady-state creep behavior for all alloy compositions. Differences in the creep behavior were observed due to the dispersion (0.5, 1.5, and 2 wt.%) of yttria, which affects the microstructure.