The alignment distribution of Nd₂Fe₁₄B grains in NdFeB sintered magnet was measured by electron back-scattering diffraction (EBSD). The alignments and the coercive force decrease ratios were calculated using these alignment distributions. These data were compared against the results obtained from magnetization measurements. From EBSD data, it was found that the alignment distributions of magnets used in this experiment were close to a Gaussian distribution. It was also found that there was no difference in the alignment distribution between magnets with Dy and without Dy. The calculated alignments using the alignment distribution functions were close to the values of magnetization measurements. However, it was found that the calculated coercive force decrease ratios were different from the results obtained from magnetization measurement.

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This study is related with the new apparatus of measuring the friction characteristic of the powder lubricant currently used in powder metallurgy, which are solid state condition. We developed the slip-type frictional tester with metal interface, and obtained the coefficient of friction more accurately than that of the ball-on-disk type friction without adhesive wear. Static and kinetic coefficients of friction are obtained from 0.23 to 0.36, and wax lubricants tend to show the value higher than that of the compounds containing metal soap.

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The aluminum sludge is transferred into α – alumina crystal structure by heat treatment. In this paper, from view point of effective utilization of aluminum sludge, we conducted rolling wear test for composite sintered by spark plasma sintering using aluminum alloy powder and α – alumina sludge in order to investigate effects of surface condition and combination of roller unit on rolling wear. The experimental results were validated by analysis of shear stress distribution under Hertz contact pressure by Finite Element Method (FEM). As result of rolling wear test using same material combination, rolling wear life of large surface pitch improved. From computing shear stress distribution by FEM, maximum shear stress value of large surface pitch showed low value in comparison to the small surface pitch. Next, in the case of rolling wear test using different materials combination of aluminum alloy only and composite including α – alumina sludge 2 %, rolling wear life of composite was shorter than the aluminum alloy only. As a result of shear stress distribution by FEM, occurrence of crack around the α – alumina sludge at near surface was predicted. It was found that the stress distribution related with crack occurrence was different in terms of combination of rolling materials.

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Prevention of cracks during compaction is one of the most important quality issues in PM industry. Therefore,various types of the mechanisms of crack formation have been studied both from academic and practical point of view. However, the mechanism of the formation of the micro cracks, which are often formed on the boss near but not at the corner of a step, has not been clarified. In this study, to investigate the effects of compacting conditions on the micro crack formation, a powder mix of Fe – Cu – C system was compacted with a stepped die. The mechanism of the micro crack formation was discussed from the viewpoints of the experimental results and FEM analysis of powder compaction.

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[in Japanese]

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