Anisotropic HDDR Nd-Fe-B magnetic powders prepared directly from strip casting alloy flakes

The effects of strip casting (SC)-hydrogenation, disproportionation, desorption, and recombination (HDDR) process parameters on the microstructures of Nd-Fe-B alloy flakes and the magnetic properties of HDDR powders are investigated. The results indicate that the alloy flakes prepared by SC speed of 3 m/s display the optimized microstructure. From this as-cast alloy flakes, anisotropic magnetic powders can be prepared by a slow recombination treatment during the HDDR. The hydrogen pressure of slow recombination treatment (HPSR) has an important influence on the microstructures and magnetic properties of powders. The remanence B-r, coercivity H-cj and magnetic energy product (BH)(max) of the magnetic powders all increase firstly, and then decrease with increasing HPSR. While the HPSR is 0.3 bar, the magnetic properties of the powders reach the maximum values of B-r = 1.3 T, H-cj = 954.3 kA/m, (BH)(max) = 259 kJ/m(3), respectively. Our results confirm that highly anisotropic HDDR magnetic powders prepared directly from the as-cast SC alloy flakes without any heat treatment can be obtained. (C) 2009 Elsevier B.V. All rights reserved.