Microstructure Evolution and Mechanical Properties of ODS FeCrAl Alloys Fabricated by Spark Plasma Sintering

Oxide dispersion strengthened (ODS) FeCrAl alloys were regarded as one of the candidate materials for accidenttolerant fuel (ATF) cladding. However, the strength-ductility tradeoff was an essential problem to limit the nuclear application. Herein, ODS FeCrAl alloys with superior mechanical properties were successfully fabricated through mechanical alloying (MA) and spark plasma sintering (SPS). The effect of mechanical alloying time on the microstructure evolution and mechanical properties in ODS FeCrAl alloys were investigated. Microstructural characterization showed that the average size of grains and nano-oxides decreased, and the density of nanooxides increased gradually, as the milling time increased. Mechanical properties revealed that increasing the milling time synergistically enhanced the strength and elongation significantly. The bimodal grain distribution with large dislocation density differences among coarse and fine grains was beneficial for the activation of the back stress strengthening and the annihilation of these microcracks, thus achieving the excellent total elongation (27.3 %+/- 0.4 %). In addition, high-density nano-oxides (9.61 x 1022/m3) was crucial for improving the ultimate strength of ODS FeCrAl alloys (964 MPa +/- 34 MPa). The strengthening mechanism superposition, based on the model of nano-oxides interrelated with dislocations, illustrated good agreement with experimental results from yield strength. To sum up, ODS FeCrAl alloy (milled for 40 h, and sintered at 1100 degrees C) presented the superior mechanical properties among various Fe alloys and ODS steels.