Development of Low Cost Rare-earth Permanent Magnets With High Energy Products

本研究的目的是在现有的多种稀土元素中选择低成本的R元素，以开发低成本的R- fe - b永磁体。用于此目的的良好候选稀土元素是所谓的“钕”族，它是Nd， Pr和Ce的混合物。这样一来，钕就丰富而便宜了。有人可能会说，混合金属也将是丰富和廉价的，是低成本R-Fe-B磁铁的良好候选者。但据报道，镧是杂金属的主要成分，不形成R铁B化合物。因此，钕将是更好的候选者。采用Fe33.5%-(5%Ce-didymium)-1% b合金制备的最佳磁性能为Br=13.2kG, Hc=10.2kOe, (BH)max=320kJ/m（40MGOe）。5% ce -钕及其合金的iHc温度依赖性与Fe-33.5% Nd-1%B合金的iHc温度依赖性基本相同。Ce作为助烧剂在合金致密化过程中发挥了重要作用，降低了（NdPr） feb化合物的熔点，使其在104℃的较低温度下烧结成为可能。在经济上，40%Ce-didymium合金是最便宜的，并且给出27MGOe的能量产物，但是具有较高的温度系数。在100℃时，40%Ce- didymium合金的iHc迅速下降，约为室温iHc的65%。另外，在目前研究的低成本合金中，（BH）max=320kJ/m的5% ce - didyum - fe - b铁氧体是最有前途的。钕铁硼磁铁合金也可用作粘结磁铁的磁粉。

The purpose of the present investigation is to develop the low cost R-Fe-B permanent magnets in selectiing the low cost R elements among available various rare-earth elements. Good candidate rare-earth elements for this purpose is the family of so called "didymium" which is the mixture of Nd, Pr, and Ce. The didymium is then abundant and inexpensive. One might say that a mischmetal will be also abundant and inexpensive, and is the good candidate for low cost R-Fe-B magnets. But it is reported that La, which is the main constituent of mishmetal, does not form the R Fe B compounds. Thus, didymium will be better candidate.The best magnetic properties obtained in present studies are Br=13.2kG, Hc=10.2kOe, and (BH)max=320kJ/m(40MGOe) with Fe33.5%-(5%Ce-didymium)-1%B alloy. Temperature dependence of iHc of5%Ce-didymium and didymium alloys arealmost same as that of the Fe-33.5% Nd-1%B alloy.Ce play an important role in densification of the alloy as sintering aid, and in lowering the melting point of (NdPr) Fe B compounds and making it possible to sinter at relatively low temperatures of 104'C. Economically, 40%Ce-didymium alloys are most inexpensive, and give the energy products of 27MGOe, but have the high temperature coefficient. The iHc of 40%Ce- didymium alloy decrease rapidly, by about 65% of iHc of the room temperature, at 100'C. Alternatively, 5%Ce-didymium-Fe-B sin ter-ed magnets with (BH)max=320kJ/m, are most promising among the present studied low cost alloys.Didymium-Fe-B magnet alloys are also available magnetic powders for bonded magnets.