We compared pure copper fabricated by PBF-LB and CSAM. For PBF-LB, spherical powders produced by gas atomization were used, and for CSAM, spherical and irregularly shaped powders produced by gas atomization, water atomization, and high-pressure water atomization using swirl water jet were used. The feedstock powder for PBF-LB should be a spherical gas-atomized powder with low phosphorus and oxygen content. At an energy density of 292.7 J/mm³ during molding, a relative density of 98.66 %, conductivity of 97.1 %IACS, tensile strength of 243 N/mm², and elongation of 60 % were obtained in the as-built condition. CSAM exhibited elongation with after-heat treatment temperature at 743 K, and a relative density of 99.05 % and conductivity of 101.3 %IACS, which were higher than those of the PBF-LB. And the relative density decreased with the after-heat treatment temperature at 853 K, but the tensile strength and elongation were equivalent to those of the PBF-LB. The feedstock powder for CSAM can be used regardless of the atomization method as long as the phosphorus content is low. And it was found that CSAM could obtain physical properties equivalent to or better than those of PBF-LB by after-heat treatment at 743-853 K.

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The growing awareness of global environmental preservation requires lighter transportation equipment, and the use of multi-materials and precision assembly and joining methods are being considered. In addition, joining methods that achieve high joining strength with low energy are desired. This article introduces three examples of joining methods that utilize metal salt formation and decomposition reactions. As the first example, the joining of aluminum and titanium, which is both lightweight and high-strength, is discussed. As the second joining example, direct joining of heat-resistant steel used for turbine blades is discussed. As the third joining example, the direct joining of copper with copper powder, which is a joining material for electronic components that control various controls in automobiles, is discussed.

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Applications of a unique high temperature optical microscopic observation system to the evaluation of plasma sprayed environmental barrier coatings (EBCs) for SiC/SiC composites in jet engines are introduced. Concept of the developed system using a light source with shorter wave length than that of thermal radiation and a band-pass filter cutting off the radiation light is illustrated. The system is used for the in-situ observation of an amorphous mullite environmental barrier coating while it is heated from 25℃ to 1400℃. The system detects the critical moment of mud-cracking which occurs at 1000℃ by the shrinkage due crystallization. Digital image correlation (DIC) provides strain mapping which indicates that large principal strain is induced along the mud-cracks, showing the cracking moment more clearly. Another application of the system is the measurement of coefficient of thermal expansion (CTE) in the in-plane direction of coatings. Thermal strain is measured from a series of images of a self-standing EBC at various temperatures using DIC and then converted to the CTE. For cases in which a self-standing coating cannot be obtained, a measurement method for a coating adhered to a substrate is also proposed.

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In recent years, to reduce the environmental impacts, replacing electric vehicles from conventional vehicles, there is a demand for improving performance of magnetic materials. In particular, soft magnetic materials are required to have high performance and a high degree of design freedom. Our research group uses soft magnetic nanoparticles as a starting material, performs high packing density without changing the particle size using the cold-spray technique. In this paper, as the first step, we examined Fe-Ni soft magnetic nanoparticles with high oxidation resistance can be fabricated in high packing density using the cold-spraying. The packing density of the particles was estimated to be 78%, which was 20% larger than the conventional compression molding at room temperature. These is not observed the sintering of the Fe-Ni nanoparticles and the size of the particles was maintained after cold spraying. The permeability, one of the magnetic properties, was increased with the packing density of the particles. These results demonstrated that the cold-spray technique is suitable for fabricating bulk-like structures using the soft magnetic nanoparticle materials.

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Carbon fiber reinforced plastics (CFRP) have been widely used in various industries as an excellent composite material that provides both light weight and high mechanical performance. In the aerospace industry, the latest generation of aircraft is replacing conventional aluminum alloys with CFRP. However, the major drawback of CFRP is their high electrical resistivity due to the insulating polymer matrix, which can result in severe damage from lightning strikes during flight. To address this issue, the surface of the CFRP aircraft body needs to have an electrically conductive path. Recently, cold spray (CS) process has been studied as a potential solution for metallizing CFRP to add electrical conductivity to the surface. This paper presents the recent contributions to the research on cold spray metallization of polymer matrix composites, including the research result of the author′ s group.

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