View the article online for updates and enhancements. Related contentCasting technology for ODS steelsdispersion of nanoparticles in liquid metals M Sarma, I Grants, I Kaldre et al. Abstract. The formation of stainless ODS steel by internal oxidation of as-cast steel has been investigated. An alloy (Fe-16Cr-0.2Al-0.05Y, wt.%) was embedded in a (VO/V 2 O 3 ) powder mixture serving as an oxygen activity buffer and heat treated at 1450°C for 20 h. After this procedure no oxide scale was present on the surface of the sample but a zone of internal oxidation with a depth of about 2000 µm was formed in its interior. The precipitates within this zone consisted of two types of oxides. Discrete aluminium oxide particles with a size of a few micrometres were formed in outer regions of the specimen. Finer aluminium-yttrium oxides with a size of some hundred nanometres were mainly precipitated in inner regions of the sample. The results can be considered as a promising step towards an alternative production route for ODS steels. IntroductionReduced activation ferritic-martensitic (RAFM) steels are promising candidate materials for structural applications in fusion reactors. These steels have been developed based on massive industrial experiences of ferritic/martensitic steel [1]. RAFM steels have interesting properties such as low sensitivity to irradiation-induced swelling and helium embrittlement [2].RAFM steels are very attractive structural materials but their high-temperature strength is limited and one of the effective approaches to solve this issue is oxide dispersion strengthening (ODS) method [3]. The nano-sized oxide particles with high number density can act as pinning points to dislocation movement [4]. Dispersed nano-sized oxides may provide a large number of trap sites for transmutant helium and radiation-induced defects [5]. The improved creep resistance and fatigue strength at high temperatures is another advantage of ODS steels [6].The typical procedure for manufacturing ODS steels is the powder metallurgy route in which steel powders and Y 2 O 3 powders are mechanically alloyed by high energy milling. The input oxides remain unmixed but they are dispersed throughout the microstructure of the alloy [7]. This technique was first developed by J. S. Benjamin and published in 1970 [8].The next step in this route is hot isostatic pressing (HIP). In HIP process, the simultaneous application of a high pressure at elevated temperatures in a constructed vessel is planned for hot compaction of the powders. The pressure inside HIP chamber is generated usually by applying purified argon gas. In the later steps after HIP, the deformed powders are hot extruded or rolled for the desired shape.

There are many works on annealing process of SPDed bulk metals but there are limited works on annealing process of SPDed sheets. Therefore, in this study the annealing response after constrained groove pressing (CGP) of low carbon steel sheets has been investigated. These sheets are subjected to severe plastic deformation at room temperature by CGP method up to three passes. Nano-structured low carbon steel sheets produced by severe plastic deformation are annealed at temperature range of 100 to 600 °C for 20 min. The microstructural changes after deformation and annealing are studied by optical microscopy. The effects of CGP strain and annealing temperature on microstructure, strength and hardness evolutions of the nano-scale grained low carbon steel are examined. The results show that annealing phenomena can effectively improve the elongation of process sheets with preserving the hardness and mechanical strength. Also, a thermal stability of microstructure can be observed with annealing at a temperature range of 375–425 °C and 400 °C is achieved as an optimum annealing temperature. Microstructure after post-annealing at temperatures of higher than 600 °C shows abnormal grain growth.

A significant step in color image compression is to apply a color space transformation to the original RGB image to concentrate most of its energy in one plane. Standard JPEG-based compression methods utilize predefined transformations like RGB to YCbCr. In this paper, a devised algorithm is proposed to optimize the transformation for each image. The algorithm iteratively increases the energy concentration by optimizing a novel cost function while limiting the matrix determinant to a bounded region.

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