HDDR処理法とNd-Fe-B系異方性磁石粉末に関する研究

抄録

Magnetic properties and microstructures of Nd-Fe-B magnet powders produced by two different hydrogen treatments were studied. One of the hydrogen treatment is a selective hydrogen decrepitation (HD) process and the other is the hydrogenation decomposition desorption recombination (HDDR) process, which is a new production process for high-performance Nd-Fe-B magnet powder. The anisotropic magnet powders produced by the selective HD process possess high coercivities, but coercivities of green compacts of the powders are very low. High-coercivity Nd-Fe-B magnet powders were produced by the HDDR process. The substitution of Fe with Co and the addition of elements such as Ga, Zr, Nb, Hf and Ta was found to be very effective for enhancing magnetic anisotropy of HDDR magnet powders. Typical magnetic properties of anisotropic bonded magnet made from HDDR magnet powders are Br=9.4 kG, iHc = 13.3 kOe and BHmax = 20.1 MGOe. Magnetic properties of anisotropic HDDR magnet powders depend on the powder particle size, and the particle size for the highest magnetic properties is 45-212 μm. It was found that the powder particles of anisotropic HDDR magnet powder consist of fine Nd₂(Fe, Co)₁₄ B crystals of the size of about 0.3 μm, and boundary-layer phase is essentially absent.