Abstract: Reduced activation ferritic Fe–14 wt%Cr and Fe–14 wt%Cr–0.3 wt%Y 2 O 3 alloys were produced by mechanical alloying and hot isostatic pressing followed by forging and heat treating. The alloy containing Y 2 O 3 developed a submicron-grained structure with homogeneous dispersion of oxide nanoparticles that enhanced the tensile properties in comparison to the Y 2 O 3 free alloy. Strengthening induced by the Y 2 O 3 dispersion appears to be effective up to 873 K, at least. A uniform distribution of Cr-rich precipitates, stable upon a heat treatment at 1123 K for 2 h, was also found in both alloys.
Abstract: In this work the spark plasma sintering (SPS) technique has been explored as an alternative consolidation route for producing ultra-fine grained Fe–14Cr model alloys containing a dispersion of oxide nanoparticles. Elemental powders of Fe and Cr, and nanosized Y2O3 powder have been mechanically alloyed in a planetary ball mill and rapidly sintered in a spark plasma furnace. Two alloys, with nominal compositions Fe–14%Cr and Fe–14%Cr–0.3%Y2O3 (wt.%), have been fabricated and their microstructure and mechanical properties investigated. The results have been compared with those obtained for other powder metallurgy processed alloys of the same composition but consolidated by hot isostatic pressing. The SPS technique under the present conditions has produced Fe–14Cr materials that apparently exhibit different microstructures yielding inferior mechanical properties than the counterpart material consolidated by hot isostatic pressing. Although the presence of a dispersion of Y-rich particles is evident, the oxide dispersion strengthened (ODS) Fe–14Cr alloy consolidated by SPS exhibits poor tensile properties. The extensive decoration of the powder particle surfaces with Cr-rich precipitates and the residual porosity appear to be responsible for the impaired properties of this ODS alloy consolidated by SPS.
Abstract: Oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steels, have been considered as promising materials for application in fusion power reactors up to about 750 °C. Four ODS RAF steels, with compositions of Fe–13.5Cr–2W–(0–0.2–0.3–0.4)Ti–0.3Y2O3 (in wt.%) were produced by powder metallurgy technique. For the different Ti-contents, the correlation between microstructure and mechanical properties was analyzed by means of scanning electron microscope (SEM) and transmission electron microscope (TEM) equipped with energy- dispersive X-ray spectrometer (EDX) and electron energy loss spectrometer (EELS). A bimodal grain size distribution was observed in all as-hipped Ti-containing ODS alloys. These alloys consisted of coarse grains typical ranging from 1 μm to 8 μm and fine grains well below 1 μm in diameter. The addition of Ti resulted in the formation of spherical Ti oxides rather than Cr oxides owing to the stronger affinity of Ti. The influence of Ti on particle size refinement was striking and the optimum effect was obtained when adding 0.3% Ti. Generally the hardness increased consistently with increasing in Ti content. The ODS alloying with 0.3% Ti exhibit the highest strength due to the optimum refinement of mean ODS particle size.
Abstract: Ferritic ODS 14Cr steels are one of the options for future nuclear and non-nuclear energy applications, in particular for components exposed to higher operation temperatures. In order to better exploit the potential advantages of ODS ferritic steels, such as improved creep strength and damage tolerance (with respect to non-ODS high-chromium steels) along with excellent oxidation resistance, a broader scientific and technical background is required. The present collaborative approach aimed to contribute to this background with respect to both fabrication issues and nano-/microstructurally based understanding of the resulting properties. In particular, the feasibility of ODS steel fabrication by means of spark plasma sintering on a semi-industrial scale was to be demonstrated. Parameter variations related to mechanical alloying, consolidation and thermal/mechanical treatments were covered. Hot extrusion was successfully applied to produce a 2.5 kg batch of ODS steel. Spark plasma sintering was scaled up towards semi-industrial 0.5 kg batches. A set of characterization techniques including Small-Angle Neutron Scattering, Transmission Electron Microscopy, Atom-Probe Tomography, Electron Probe Micro-Analysis, Electron Back-Scatter Diffraction and Transmission Kikuchi Diffraction as well as mechanical testing were applied to characterize the materials at different scales and stages of the fabrication process and to underpin the findings, such as a pronounced bimodality of grain size distributions, by observation-based understanding.
Abstract: A Fe–14Cr–1W–0.4Ti–0.3Y203 ferritic steel bar was characterised by different microstructural techniques in order to evaluate the link between its microstructure and the mechanical properties achieved. This bar was produced by mechanical alloying of a pre-alloyed gas atomised powder with yttria particles, followed by hot extrusion and subsequently annealing. The knowledge of the microstructure of this 14Cr oxide dispersion strengthened (ODS) steel allows for the explanation of the mechanical properties observed, such as the decrease of the ductility found in the transverse orientation of the bar, the existence of zig-zag crack paths in the broken specimens after the impact tests at low temperatures and the appearance of delaminations when the temperature is increased.
Abstract: Oxide dispersed strengthened steels can exhibit a strongly anisotropic microstructure with elongated pancake-like grains in the rolling plane. This gives rise to intergranular fracture and subsequent delamination along large-area grain boundaries. We investigated an oxide dispersed strengthened alloy with 12 mass percent Cr, manufactured by mechanical alloying, hot extrusion and cold rolling by means small punch tests and subsequent fractographic analysis. The fracture behaviour was analysed in dependence of the specimen orientation. The results from small punch tests were contrasted with those from impact tests with sub-sized samples. In both tests, the ductile to brittle transition temperatures as well as the upper shelf energies depend significantly on the orientation of the specimens. However, the delamination affects the fracture of impact and small punch test samples in different ways. Thus, it depends on the load situation whether delamination has a beneficial or a detrimental effect on the fracture behaviour.
TL;DR: WinPLOTR is a graphic program for the analysis of powder diffraction patterns that has been developed for a Windows 9x/2k/NT environment and can be used as a Graphic User Interface for programs defined by the user.
Abstract: WinPLOTR is a graphic program for the analysis of powder diffraction patterns. It has been developed for a Windows 9x/2k/NT environment. It takes advantage of this graphical environment to offer a powerful and user-friendly powder diffraction tool. The program is able to display and analyse many different kinds of diffraction patterns as well as calculated and observed profiles coming from the Windows/DOS version of the program FullProf. It can also be used as a Graphic User Interface (GUI) for programs defined by the user.
Abstract: The use of the Voigt function for the analysis of the integral breadths of broadened X-ray diffraction line profiles forms the basis of a rapid and powerful single-line method of crystallite-size and strain determination which is easy to apply. To avoid graphical methods or interpolation from tables, empirical formulae of high accuracy are used and an estimation of errors is presented, including the influence of line-profile asymmetry. The method is applied to four practical cases of size-strain broadening: (i) cold-worked nickel, (ii) a nitrided steel, (iii) an electrodeposited nickel layer and (iv) a liquid-quenched AlSi alloy.
Abstract: Oxide dispersion strengthened (ODS) steels are the most promising class of materials with a potential to be used at elevated temperature under severe neutron exposure environment. Leading technology development of ODS steels has been conducted at the Japan Nuclear Cycle Development Institute (JNC) particularly emphasizing fuel cladding application for fast reactors. This paper reviews the JNC’s activities on ODS steel development as ‘nano-composite materials’. Martensitic 9Cr-ODS and ferritic 12Cr-ODS steels have been successfully developed; Y2O3 oxide particles can be controlled on a nano-scale and high-temperature properties were noticeably improved through controlling the grain boundary structure on an atomic scale. The ODS-technology development achieved in the field of fast reactors should be effectively spun off to the fusion reactor first wall and blanket structural materials to allow for safe and economical reactor design.
"Microstructure and mechanical prope..." refers background in this paper
...Fe–Cr binary alloys are nowadays the most promising base to fabricate reduced-activation ferritic/martensitic (RAFM) and ferritic (RAF) steels for structural applications in future fusion reactors as well as in generation IV fission reactors [1–3]....
Abstract: Oxide dispersion-strengthened (ODS) steels are being developed and investigated for nuclear fission and nuclear fusion applications in Japan, Europe, and the United States. In addition, commercial ODS products are available and have been used in niche applications. Microstructural and mechanical properties studies have been conducted at Oak Ridge National Laboratory and elsewhere on various commercial and experimental ODS steels. Tensile and creep properties have been obtained and collected from literature and commercial sources. These data are compared to show the differences and similarities of different ODS steels, and observations are explained in terms of the microstructures of the steels.