Fabrication And Property Study Of The Oxide Dispersion Strengthened Ferrite Alloy

As one of the most promising materials for the fuel cladding and blanket materials of the future supercritical water reactor (SCWR), oxide dispersion strengthened (ODS) ferritic steels have attracted a lot of attention of researchers for their excellent high temperature performance and resistance to radiation and void swelling. The production process and comprehensive properties of a reduced activation oxide dispersion strengthened ferritic steel with nominal composition of Fe-12Cr-2.5W-0.2Ti-0.25Y2O3(designated12Cr-ODS) were investigated in this study.According to the working conditions of ODS alloys, the spherical base alloy powder with optimized composition design was prepared through atomization. Y2O3powder was added into the base alloy powder with different size by pre-dispersing process, during which the Y2O3powder was coated on the spherical base alloy powder and dispersed uniformly in the following mechanical alloying (MA) and spark plasma sintering (SPS). Therefore, alloy sample with uniform composition and excellent comprehensive properties was prepared. Moreover, the mechanical properties of the sample changed with the improved microstructure of refining grains and optimised oxide particles that were acquired through annealing.The SPS is considered as the process cooperated by particle discharging, heat conduction and mechanical pressure. The on-off DC pulse electrification generates:(1) spark plasma,(2) impact pressure,(3) joule heating, and (4) an electrical-field diffusion mechanism, which make the sintering sample under a synergic multi-field effect. In this study, the densification mechanism of12O-0DS alloy in the SPS process and the influence of plasma generated by pulsed current in this process was investigated.The hot deformation behavior of the as-prepared12Cr-ODS alloy was studied through the thermal simulation experiment under the temperature of1100～1200℃, the strain rate of10-1～10-3/s. The microstructure transformation and the second phase particle migration under hot deformation were studied by electron back scattering diffraction (EBSD) experiment. Moreover, typical dynamic response characteristics were showed through the analysis of the true stress-strain curve. The core of the dispersion strengthening lies in the orderly distribution of particles with different size and composition. The constitution and formation of the dispersed phase in the as-prepared12Cr-ODS alloy was oberserved and analyzed.3kinds of formation mechanisms including diffusion mechanism, dissolving precipitation mechanism and the secondary precipitation mechanism were determined.The addition of Fe-Al intermetallic compound powder in the12Cr-ODS alloy was studied. Compared with the alloy without Fe-Al particles, this new ODS alloy with addition Fe-Al particles of prepared by the above process showed better comprehensive properties, especially the oxidation resistance due to the synergistic effect of the2types of dispersed particles.