ODS-materials for high temperature applications in advanced nuclear systems

AbstractA ferritic ODS-alloy (Fe-14Cr-1W-0.25Ti) has been manufactured by application of the powder metallurgical production route involving at first mechanical alloying of ∼10kg pre-alloyed steel powder together with an Y2O3 addition for 12h in a high energy industrial ball mill under hydrogen atmosphere at the company ZOZ GmbH. As a next step, one part of the alloyed powder was hot extruded into rods while another portion was hot isostatically pressed into plates. Both materials were then heat treated. A characterization program on these ODS-alloy production forms included microstructural and mechanical investigations: SANS and TEM assume the existence of Y2Ti2O7 nano clusters and show a bimodal distribution of ODS-particle sizes in both ODS variants. EBSD maps showed a strong 〈110〉 texture corresponding to the α fiber for the hot extruded ODS and a slight 〈001〉 texture for the hipped ODS material. Fracture toughness tests in different specimen orientations (extruded ODS) with mini 0.2T C(T) specimens together with Charpy impact tests revealed anisotropic mechanical properties: Promising (fracture) toughness levels were obtained in the specimen orientation perpendicular to the extrusion direction, while the toughness levels remained low in extrusion direction and generally for the hipped ODS material at all test temperatures. The fracture toughness tests were performed according to ASTM E 1921 and 1820 standards

Microstructure and mechanical properties of an ODS RAF steel fabricated by hot extrusion or hot isostatic pressing

Ingots of an oxide dispersion strengthened reduced activation ferritic steel with the Fe-14Cr-2W-0.3Ti-0.3Y(2)O(3) chemical composition (in wt.%) were synthesized by mechanical alloying of elemental powders with 0.3 wt.% Y2O3 particles in a planetary ball mill, in a hydrogen atmosphere. and compacted by either hot extrusion or hot isostatic pressing. The microstructures of the obtained materials were characterized by means of light microscopy, transmission electron microscopy and chemical analyses. The mechanical properties were evaluated by means of Vickers microhardness measurements and tensile tests. It was found that the microstructure of both materials is composed of ferritic grains having a submicron size and containing nanometric Y-Ti-O oxide particles with a mean size of about 10 nm, uniformly distributed in the matrix. The oxide particles in the hot extruded steel were identified as YTiO3 phase. In larger (>10 nm) oxide particles Cr was found next to Ti, Y and O. The steel produced by hot extrusion exhibits much higher tensile strength and hardness at low to moderate temperatures, as compared to the steel fabricated by hot isostatic pressing, which was mainly attributed to smaller pores but also to more severe work hardening in the case of the hot extruded steel. (C) 2011 Elsevier B.V. All rights reserved

Impact of materials technology on the breeding blanket design – Recent progress and case studies in materials technology

A major part in the EUROfusion materials research program is dedicated to characterize and quantify nuclear fusion specific neutron damage in structural materials. While the majority of irradiation data gives a relatively clear view on the displacement damage, the effect of transmutation – i.e. especially hydrogen and helium production in steels – is not yet explored very well. However, few available results indicate that EUROFER-type steels will reach their operating limit as soon as the formation of helium bubbles reaches a critical amount or size. At that point, the material would fail due to embrittlement at the considered load. This paper presents a strategy for the mitigation of the before-mentioned problem using the following facts: • the neutron dose and related transmutation rate decreases quickly inside the first wall, that is, only a plasma-near area is extremely loaded • nanostructured oxide dispersion strengthened (ODS) steels may have an enormous trapping effect on helium and hydrogen, which would suppress the formation of large helium bubbles • compared to conventional steels, ODS steels show improved irradiation tensile ductility and creep strength In summary, producing the plasma facing, highly neutron and heat loaded part of blankets by an ODS steel, while using EUROFER97 for everything else, would allow a higher heat flux as well as a longer operating period. Consequently, we (1) developed and produced 14 % Cr ferritic ODS steel plates. (2) We fabricated a mockup with 5 cooling channels and a plated first wall of ODS steel, using the same production processes as for a real component. And finally, (3) we performed high heat flux tests in the HELOKA facility (Helium Loop Karlsruhe at KIT) applying short and up to 2 h long pulses, in which the operating temperature limit for EUROFER97 (i.e., 550 °C) was finally exceeded by 100 K. Thereafter, microstructure and defect analyses did not reveal defects or recognizable damage. Only a heat affected zone in the EUROFER/ODS steel interface could be detected. This demonstrates that the use of ODS steel could make a decisive difference in the future design and performance of breeding blankets

Fabrication routes for advanced first wall design alternatives

In future nuclear fusion reactors, plasma facing components have to sustain specific neutron damage. While the majority of irradiation data provides a relatively clear picture of the displacement damage, the effect of helium transmutation is not yet explored in detail. Nevertheless, available results from simulation experiments indicate that 9%-chromium steels will reach their operating limit as soon as the growing helium bubbles extent a critical size. At that point, the material would most probably fail due to grain boundary embrittlement. In this contribution, we present a strategy for the mitigation of the before-mentioned problem using the following facts. (1) The neutron dose and related transmutation rate decreases quickly inside the first wall of the breeding blankets, that is, only a plasma-near area is extremely loaded. (2) Nanostructured oxide dispersion strengthened (ODS) steels may have an enormous trapping effect on helium, which would suppress the formation of large helium bubbles for a much longer period. (3) Compared to conventional steels, ODS steels also provide improved irradiation tensile ductility and creep strength. Therefore, a design, based on the fabrication of the plasma facing and highly neutron and heat loaded parts of blankets by an ODS steel, while using EUROFER97 for everything else, would extend the operating time and enable a higher heat flux. Consequently, we (i) developed and produced 14%Cr ferritic ODS steel plates and (ii) optimized and demonstrated a scalable industrial production route. (iii) We fabricated a mock-up with five cooling channels and a plated first wall of ODS steel, using the same production processes as for a real component. (iv) Finally, we performed high heat flux tests in the Helium Loop Karlsruhe, applying a few hundred short and a few 2 h long pulses, in which the operating temperature limit for EUROFER97 (i.e. 550 ◦C) was finally exceeded by 100 K. (v) Thereafter, microstructure and defect analyses did not reveal critical defects or recognizable damage. Only a heat affected zone in the EUROFER/ODS steel interface could be detected. However, a solution to prohibit the formation of such heat affected zones is given. These research contributions demonstrate that the use of ODS steel is not only feasible and affordable but could make a decisive difference in the future design and performance of breeding blankets

Analysing Port Community System Network Evolution

Ports have played an important role in facilitating exchanges among countries since the day when inland transportation was poor. As ports become hubs for global supply chain, they have to maintain their competitiveness not only by reassuring their efficiency, reliability, accessibility to hinterland, and sustainability. In addition, there is a constant challenge from all operational parties of the port to acquire needed information or to trust information received, due to multiple legacy systems and platforms that do not integrate with each other, and to the lack of real time updates. There are differing agendas between parties and, sometimes, distrust within the multi-stakeholder ecosystem leads to working in silos. This jeopardises seamless data exchange and cooperation across the port value chain, resulting in significant inefficiencies. Port community system (PCS) can enhance communication and simplify administrative process resulting economic and environmental benefit for actors in the supply chain. The invisibility of the benefit, actors’ heterogeneity and significant investment to develop the system resulting a reluctance in implementing PCS. This chapter aims to study the evolution mechanism behind the process of PCS network development using lessons learned from industrial symbiosis network development and network trajectories theory. The PCS network development follows a serendipitous and goal-oriented process that can be categorised into three stages: pre-PCS network, PCS network emergence, and PCS network expansion. This chapter contributes to the exploration of network evolution and documents lesson learned to foster PCS implementation.© 2020 Springer. This is a post-peer-review, pre-copyedit version of an article published in European Port Cities in Transition: Moving Towards More Sustainable Sea Transport Hubs. The final authenticated version is available online at: http://dx.doi.org/10.1007/978-3-030-36464-9_10fi=vertaisarvioitu|en=peerReviewed

Reply to "comments on 'The mechanisms of the fcc-bcc martensitic transformation revealed by pole figures'"

Bhadeshia recently claimed that the two-step theory of martensitic transformation was mathematically incorrect and incapable of making predictions about the observed pole figures. The present paper argues that his comments are not justified and that his alternative propositions do not agree with the observations. The continuous rotations observed in the pole figures do not result from the tempering treatments but from the plastic accommodation of the lattice transformation during the γ → → α sequence. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

About the influence of nano-precipitation and cold- working on the recrystallization mechanisms in ferritic ODS materials

International audienceOxide dispersion strengthened (ODS) ferritic steels are promising candidates for high burn up fuel pins of Sodium Fast Reactors and structural components of fusion reactor. They are elaborated by powder metallurgy and their manufacturing route is complex and specific, including hot forming and cold working. Different heat treatments are necessary to recrystallize these materials and to relieve internal stresses. The presence of highly stable nano-oxydes and the limited stored energy after consolidation can make the recrystallization temperature extremely high (> 0.9 Tmelting). It is well known that cold working largely favours the occurrence of recrystallization in metals by increasing the stored energy. Here, a generic study conducted on the recrystallization mechanisms in ODS materials is presented. Model grades with different amounts of nano-particles were elaborated and submitted to annealing after consolidation and after subsequent cold-working. It comes out that the recrystallization mechanisms are strongly influenced by both the cold-working and the nano-particles population. According to the initial amount of nano-particles incorporated, their chemical nature can change. In the as-received state, after consolidation, extended recovery by subgrain growth can be observed if nano-oxides particles strongly coarsened. Otherwise, materials remain highly stable and no recovery is measured. After cold-working, discontinuous recrystallization occurs in all the grades and a grain growth stage after primary recrystallization can be noted if particles coarsened