Nd2Fe14B磁石合金の焼結特性に及ぼすCo添加の影響

概要

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Effects of Co addition on sintering behavior of NdFeB ternary alloy powder were investigated through observation of microstructure and measurements of DTA and linear shrinkage. In the case of NdFeB powder, shrinkage started at 940K corresponding to the appearance of a liquid phase, which was derived from ternary eutectic reaction between Nd-rich, Nd2Fe14B and Nd1.1Fe4B4 phase. Although the shrinkage below 1273K was very small because of a lack in the amount of the liquid phase, remarkable shrinking occured when sintering temperature was raised above 1273K. This is probably due to increase of the amount of the liquid phase formed by the eutectic and peritectic reactions between Nd-rich, Nd2Fe14B and Nd1.1Fe4B4 phase. In the case of Co addition the starting point of shrinkage as well as that of remarkable shrinking shifted to a lower temperature than the NdFeB ternary specimen. This can be explained by the formation of the liquid phase derived from Nd-Co compounds.