Correlation of the energy product with evolution of the nanostructure in the Y,Dy,Nd-(Fe, Co)-B magnetic alloy

TitleCorrelation of the energy product with evolution of the nanostructure in the Y,Dy,Nd-(Fe, Co)-B magnetic alloy
Publication TypeJournal Article
Year of Publication2009
AuthorsWu YQ, Tang W, Kramer MJ, Dennis KW, Oster N, McCallum RW, Anderson IE
Journal TitleJournal of Applied Physics
Date Published04/01
ISBN Number0021-8979
Accession NumberISI:000266633500196

The devitrification behavior of nanocrystalline MRE2(Fe, Co)(14)B+ZrC (MRE=Nd+Y+Dy) was studied using differential scanning calorimetry (DSC), synchrotron high temperature x-ray diffraction, and analytical transmission electron microscopy (TEM) techniques. Alloy ribbons were melt spun at 25 m/s to obtain an amorphous structure. Optimum hard magnetic properties (B-r = 7.2 kG, H-c=12.7 kOe and (BH)(max)=10.8 MG Oe) were obtained in ribbons annealed at 750 degrees C for 15 min. A reduced annealing temperature of 638 degrees C and holding time from 0 to 11 min were chosen based on DSC analysis. Large changes in both microstructure and hard magnetic properties were found in a narrow window of annealing time, 4.5-6 min, resulting in a dramatic increase in energy product, remanence and coercivity: 0.96 MG Oe, 5.2 kG, 2.7 kOe to 5.7 MG Oe, 7.2 kG, 8.5 kOe for (BH)(max), Br and Hc, respectively. Energy dispersive x-ray spectroscopy and energy filtered TEM analyses indicate that Zr- and C-rich particles (similar to 5 nm) and thin grain boundary layers (1-2 nm thick) are formed surrounding 2-14-1 hard phase grains when the annealing time is over 6 min. Further annealing resulted in a more distinct hard phase surrounded by a nonmagnetic grain boundary phase similar to 1 nm in thickness. The thin grain boundary layer phase starts to disappear with annealing time over 11 min. The partitioning behavior of various elements at different annealing conditions appears to be associated with significant changes in magnetic properties, leading to an improved optimum microstructure. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3067539]

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