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Abstract: The effectiveness of Al addition for improvement of the corrosion resistance of ODS steel in lead–bismuth eutectic (LBE) was investigated. Al-alloying surface treatment using a GESA facility was applied to 9Cr-ODS martensitic steel, and the corrosion resistance in stagnant LBE containing 10−6 wt% oxygen was subsequently examined. Corrosion resistance of ODS ferritic steels with high Cr content (14.7wt%), containing 3.3–3.8wt% Al and small amounts of Zr or Hf, was also examined. Al-alloying surface treated 9Cr-ODS martensitic steel was tested at 650°C and ODS ferritic steels with high Cr content, containing 3.3–3.8wt% Al and small amounts of Zr or Hf, were tested at 650 and 700°C. The maximum exposure duration was 10,000h. All tested materials showed good corrosion resistance under all test conditions. Both the Al-alloying surface treatment by the GESA facility and the Al addition to the matrix with small amounts of Zr or Hf effectively improved the compatibility of ODS steel with LBE at high temperatures. [Copyright &y& Elsevier]

Abstract: The effects of alloying elements and temperature on corrosion behavior in supercritical water (SCW) were investigated for oxide dispersion strengthened (ODS) steels to design alloy compositions for corrosion-resistant ODS ferritic steels. Corrosion tests of the ODS steels were carried out at 400, 500, and 600°C under 25MPa with 8ppm of dissolved oxygen. The addition of 4wt.%Al is effective to improve the corrosion resistance of 16Cr-ODS steel, suggesting that an adequate combination between Cr and Al content ranges (14–16)Cr and (3.5–4.5)Al. The addition of Ce or Zr to W-added ODS steel is expected to increase its corrosion resistance. At higher temperatures, the addition of 4wt.%Al to 16Cr-ODS steel induces better corrosion resistance rather than the temperature of 400°C. It is considered that for 16Cr-ODS steels with Al, the continuous alumina mainly suppresses the inward oxygen diffusion and the Fe–Cr spinel adds to the suppression of oxygen diffusion. [Copyright &y& Elsevier]

Abstract: Anisotropic fracture behavior of SOC-1 oxide dispersion strengthened (ODS) ferritic steel has been investigated for a hot-extruded bar by tensile tests and Charpy impact tests. These mechanical properties are better in the longitudinal direction than in the transverse directions against extrusion direction (ED). Fracture surface observations by scanning electron microscopy and auger electron spectroscopy indicated bundle-like morphology with existence of segregation/precipitation/inclusions along ED. Pole figures of the hot-extruded bar characterized using electron back scattering diffraction (EBSD) technique and X-ray diffraction exhibited 〈110〉 fiber texture formation along ED. The EBSD orientation map showed a complex bundle-like grain morphology which consists of elongated grains having a specific orientation 〈110〉// ED and relatively isotropic and small grains having other orientation. The results conclude that the combined effects of observed elongated grain morphology and these small grains with segregation/precipitation/inclusions along ED can explain the anisotropic fracture behavior of the hot-extruded ODS ferritic steel. [Copyright &y& Elsevier]

Abstract: The effect of aging on the ductile to brittle transition behavior of recrystallized high-Cr ODS ferritic steels were investigated using small-punch test technique. In order to reduce the anisotropy of microstructure in the as-received ODS steels, they were recrystallized after cold rolling. The ODS steel without Al hardly recrystallized at 1200°C for 90min, while the ODS steel with Al significantly recrystallized. Ductile–brittle transition curves were drawn for as received, recrystallized, and thermally aged (at 450°C for 1440h). Before aging, both materials had good impact properties with low ductile–brittle transition temperatures and high USEs. The ductile–brittle transition temperatures are not dependent of the grain size. The aging degraded their impact properties for ODS steel with Al. However, almost no degradation occurred for the ODS steel without Al. SEM observation showed an influence of the cold-rolling direction on the fracture behavior especially at low temperatures. [Copyright &y& Elsevier]

Abstract: A successful example of high-Cr oxide dispersion strengthened (ODS) steels development is introduced with showing key technologies to overcome the issues to meet material requirements for next generation nuclear systems as well as fusion blanket systems. Corrosion issue requires Cr concentration more than 14wt.%, but aging embrittlement issue requires it less than 16wt.%. An addition of 4wt.%Al is effective to improve corrosion resistance of 16wt.%Cr-ODS steel in supercritical water (SCW) and lead–bismuth eutectics (LBE), while it is detrimental to high-temperature strength. An addition of small amount of Zr or Hf results in a significant increase in creep strength at 973K in Al-added ODS steels. Feasibility of high-Cr ODS steel without Al addition is assessed for fusion application in terms of corrosion resistance in SCW. [Copyright &y& Elsevier]

Abstract: The phase and metal/oxide interface structure of the nanometer-scale particles in an Al-alloyed high-Cr oxide dispersion strengthened ferritic steel extruded at 1150°C and 1050°C were characterized by high-resolution transmission electron microscopy and diffraction contrast techniques, including weak beam electron microscopy. After extrusion at 1150°C, yttrium–aluminum–hexagonal (YAH, YAlO3) and yttrium–aluminum–perovskite (YAP, YAlO3) oxides (diameter ⩽10nm) constitute ∼55% and 38% of the particles, respectively; ∼78% of the particles (4.5–10nm in diameter), which include 40% YAH oxide and 38% YAP phase with misfit (translational) moiré fringe spacing of 2.15nm and 1.65nm, respectively, are semi-coherent with the matrix. After extrusion at 1050°C, almost all the particles are YAH phase, and ∼86.5% (diameter <4.5nm) are coherent with the matrix. The coherency of the oxides is size dependent. The crystallographic orientation correlations of the oxides and matrix were found. [ABSTRACT FROM AUTHOR]