Development of a Co-free NdFeB anisotropic bonded magnet produced from the d-HDDR processed powder

The NdFeB anisotropic bonded magnet produced by the HDDR method, which was developed in 1990, has not found general popularity due to its high cost and low serviceable temperature of 353 K. The authors have developed a new production method that overcomes these barriers to decrease the cost and increase the serviceable temperature. The use of the dynamic HDDR (d-HDDR) process eliminates the need for Co, thus greatly reducing the production cost of NdFeB anisotropic bonded magnets with a (BH)max of 159 kJ/m(3). The anisotropy of the NdFeB magnetic powder is induced by the control of the reaction rate of the NdFeB alloy and hydrogen, by controlling the hydrogen pressure in the HDDR process. The serviceable temperature is increased by the addition of Dy after the application of the d-HDDR method. An increase in intrinsic coercivity, iHc, from 1.12 MA/m to 1.56 MA/m, corresponds to a proportional increase in the serviceable temperature to 413 K.