E. Materna-Morris

New method for detection of Li inside He bubbles formed in B10-alloyed steel after neutron irradiation.

Electron energy loss spectroscopy (EELS) was used to detect and study the spatial distribution on the nanoscale of He and Li in boron-alloyed steel after neutron irradiation. Li and He are the products of the (10)B(n, α)(7)Li nuclear transmutation reaction and knowledge of their distribution is important to understand their influence on mechanical properties. Here, a new method is presented for the direct detection of Li in Fe, which is based on the analysis of the plasmon structure in EELS spectra. Li drops or particles in He bubbles show pronounced Li plasmon line at 10eV which can be extracted from the Fe/Cr plasmon. The Gaussian or linear interpolation of the Fe/Cr plasmon and its subtraction allows for the calculation of Li and He two-dimensional maps and the study their spatial distribution. The analysis of Li plasmon fine structure allows imaging surface effects in the Li drops.

Intermetallic Phase Precipitation in Duplex Stainless Steels during High Temperature Exposition

The intermetallic phase precipitation, mainly sigma () and chi () phases, was studied in a comparative manner in two stainless duplex steels: a duplex type UNS S31803 and a superduplex type UNS S32520. The -phase precipitated at ferrite/ferrite grain boundaries prior to the -phase precipitation, which occurred preferentially at ferrite/austenite interfaces and at ferrite/ferrite grain boundaries. The -phase precipitation is a eutectoid type reaction of ferrite, leading to -phase and austenite (γ). The -phase precipitated at lower temperatures and in smaller amounts than sigma. The -phase is metastable in the studied steels and was consumed during the -phase precipitation.

Selective Laser Sintering as Manufacturing Process for the Realization of Complex Nuclear Fusion and High Heat Flux Components

Abstract The development of fabrication technologies for ITER and DEMO Blanket concepts is an activity followed by the KIT since a long time. A variety of fabrication technologies has been developed and qualified in strong collaboration with industry. Besides the standard technologies, an activity has been launched to explore the capabilities of generative fabrication procedures such as Laser Beam Melting (LBM) and Selective Laser Sintering (SLS). To manufacture demonstrator parts for Blankets by LBM /SLS, EUROFER (a Reduced Activation Ferritic Martensitic/RAFM steel applied e.g. in ITER) has been produced as powder metallurgical product. With this material, test parts have been realized. The test program started with solid parts and simple geometries used for extraction of specimen for material qualification purpose. Later, more complex parts were fabricated to investigate the feasibility of hollow and double walled structures and components with internal channel structures. Finally, blanket relevant part segments (e.g. for the Stiffening Plates) with meandering cooling channel structures and Flow Channel Insert segment demonstration parts for the EU Helium Cooled Pebble Bed and the Dual Coolant Lithium Lead Breeder Blanket concepts for DEMO have been fabricated. First preliminary qualification activities have been concluded using test procedures applied e.g. for the qualification of welding seams such as Tensile – and Charpy tests, macro- and micro structure investigation or hardness measurement. The findings have been compared to standard material properties of EUROFER in order to quantify the fabrication results. Material properties of ~ 80% and more, compared to standard rolled EUROFER with comparable heat treatment history could be demonstrated in case of Tensile- and Yield- strength, total strain after fracture as well as energy consumption in Charpy tests. Also the joining of generatively fabricated sub-components together with conventionally fabricated EUROFER parts by Electron Beam welding has been investigated in order to test the option of the fabrication of hybrid components. These hybrid components are intended to combine parts with straight channels fabricated by Electrical Discharge Machining together with generative fabricated parts with complex structures of cooling channels (e.g. nested U-shaped flow paths) which cannot be realized using standard machining technologies. This technical note reports the first promising qualification results of generatively fabricated EUROFER parts. Also the weldability of generative fabricated parts and conventionally fabricated EUROFER has been demonstrated. Preliminary qualification results of the welding are shown, and possibilities for experimental qualifications are discussed.

Modifications of Alloying Elements in Martensitic 8-10%Cr-Steels and its Influence of Neutron Irradiation on Material Properties

9 – 12%Cr-MoVNb steels are successful materials for the use at higher temperatures. The universal application in turbines and power plants promises an expedient material for fission and future fusion reactors. Different developmental alloys were fabricated, irradiated and mechanically tested to optimize the material properties. Already, after the first irradiation tests could be shown that this type of steel has a reduced swelling and much faster decay of radioactivity than e.g. austenitic Cr-Ni-steels. This inherent property of reduced activation includes a high recycling potential. Further variations in the chemical compositions were carried out to increase the decay of radioactivity and to reduce the hardening and strengthening by neutron irradiation. The state of development today is a 9%Cr-WVTa-alloy, which is called EUROFER. The post-irradiation behavior and the development of material matrix are shown in comparison with further test alloys. The emphasis is to characterize the hardening mechanisms by irradiation at lower temperatures, which appear in helium bubbles, interstitial loops, and α`-precipitates.