Magnetic properties and microstructure of gas atomized MRE2(Fe,Co)(14)B powder with ZrC addition (MRE=Nd plus Y plus Dy)

Gas atomization powder with Zr substitutions for the MRE and ZrC additions were systematically studied. The results show that the partial substitutions of Zr and the ZrC additions effectively improved glass formability in the alloys. Scanning electron microscopy (SEM) revealed that the as-atomized powder with a particle size of less than 32 mu m is predominately uniform equiaxed grains with an average grain size of 1.5 mu m. X-ray diffraction and differential thermal analysis measurements detected very tiny amounts of amorphous phase. After annealing at 700 degrees C for 15 min, the SEM grain microstructure exhibits a minor change, but magnetic properties are substantially improved. M versus T measurements reveal that the phase composition evolved from 2:14:1 plus a small amount of 2:17 phases to a single 2:14:1 phase during the annealing process. The sieve analysis of the powders showed a particle size distribution with 90 wt% of the powder less than 45 mu m. The magnetic properties of the annealed powder varied with particle size. (BH)(max) first increases with increasing particle size from 5 mu m, reaches the peak value in the size range of 20-25 mu m, and then decreases with increasing particle size. For the 20-25 mu m powder sample annealed at 700 degrees C for 15 min, the (BH)(max) of 9.6 MG Oe at room temperature and 5.6 MG Oe at 200 degrees C were obtained, respectively. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3073929]