The magnetic pulse welding (MPW) technique was employed for the end closure joining of fuel pin cladding tubes made of ferritic-martensitic (FM) steel and oxide-dispersion strengthened (ODS) steel. The technique is a solid-state impact joining process based on the electromagnetic force, similar to explosive welding. For a given set of optimal process parameters, e.g., the endplug geometry, the rigid metallurgical bonding between the tube and end plug was obtained by high-velocity impact collision accompanied with surface jetting. The joint region showed a typical wavy morphology with a narrow grain boundary-like bonding interface. There was no evidence of even local melting, and only the limited grain refinement was observed in the vicinity of the bonding interface without destructing the original reinforcement microstructure of the FM-ODS steel, i.e., a fine grain structure with oxide dispersion. No leaks were detected during helium leakage test, and moreover, the rupture occurred in the cladding tube section without leaving any joint damage during internal pressure burst test. All of the results proved the integrity and durability of the MPWed joints and signified the great potential of this method of end closure joining for advanced fast reactor fuel pin fabrication.
The work is devoted to the development of a Cu-Nb composite material and an approach to the design of reliable tool coils, which require a magnetic field of about 40 T with a microsecond duration. A powder method has been applied to obtain homogeneous samples from a fine Cu-Nb composite alloy. The dependence of electrical and mechanical properties on annealing temperature was investigated. Layered sample was produced and tested under conditions of high magnetic field generation in comparison with a commercial wire.
Iridium is rather difficult to process due to its brittleness and sensitivity to impurities. It is better treated while it is clean and fine-grained. Therefore, it should be promising to use fine powders. At the same time, the pressing and sintering of iridium nanopowders has not been studied well. This paper describes a method for manufacturing thin-walled iridium tubes using powder technology. Iridium powder of 99.997 % purity with an average particle size of 42 nm (BET) was obtained by the electrolysis of molten salts. It was subjected to radial magnetic pulsed compaction in copper shell, which was subsequently chemically removed. The resulting pressure on the powder here strongly depends on the parameters of the magnetic field pulse and other initial conditions, such as the properties of the shell, the thickness of the charge and the rheological properties of the powder. Therefore, the properties of green and sintered samples were investigated depending on the amplitude of the magnetic pressure, without changing the other parameters. Green bodies with a relative density of up to 50 % were obtained with an amplitude of magnetic pressure of 85 -190 MPa. The green density slightly increased with increasing magnetic pressure. Sintering at 1000°C in a hydrogen atmosphere yielded thin-walled tubes with a grain size of 0.3 μm and a density of up to 22.3 g / cm 3 , close to the theoretical density of iridium, 22.56 g / cm 3 . The sintered density was insensitive to the green density in the studied range. Solid sintered tubes were obtained by an amplitude of magnetic pressure between 85 and 122 MPa.
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