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Vol.30, No.2, 186 ~ 196, 1992

Title

Powder Characteristics and Compositional Effect on the Magnetic Properties of Nd - Fe - Co - B and Nd - Fe - Co - Zr - B Bonded Magnet

최승덕S . D . Choi, 이우영W . Y . Lee, 양충진Choog Jin Yang

Abstract

In compacting the melt-spun Nd_(14)Fe_(76)Co₄B_0 and Nd_(10.3)Fe_(79)Co₂Zr_(1.5)B_7 magnetic powders, the difference in composition induces a different behavior of closed packing rate as a function of aspect ratio of the powders. The Nd_(10.5)Fe_(79)Co₂Zr_(1.5)B_7 alloy having a low Co/Fe ratio(low density) shows the better green density to have an enhanced closed packing rate. An empirical power equation relating the green density with the compacting pressure was obtained such as ρ(g/㎤) =5.2∼5.6 × p^(0.04◎∼0.06◎)(ton/㎠). The Nd_(14)Fe_(76)Co₄B_6 alloy having a high Nd/Fe ratio possesses much finer grain size(50∼60㎚) than that of Nd_(0.5)Fe_(79)Co₂Zr_(1.5)B_7 alloy and shoves the higher coercivity(iHc=14∼15kOe). The higher Nd/Fe ratio in the melt-spun Nd-Fe-Co-B alloy, where the domain wall pinning mechanism was found to be predominant., assists the formation of Nd-rich grain boundary phase acting as a pinning site. The grain boundary ranges over 12∼16Å thick in the Nd-Fe-Co-B alloy while it ranges over 8∼12Å thick in the Nd-Fe-Co-Zr-B alloy.

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