Phase transformation sequence and magnetic properties of melt-spun SmCo-based alloy after isochronal heat treatment

Journal Article · Sat Nov 15 00:00:00 EST 2008 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3021061· OSTI ID:21185927

Xiong, X Y ^[1]; Finlayson, T R ^[2]

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1. Monash Centre for Electron Microscopy and Department of Materials Engineering, Monash University, Victoria 3800 (Australia)
2. School of Physics, University of Melbourne, Victoria 3010 (Australia)

The phase transformation sequence, microstructure and compositions, and magnetic properties for a melt-spun Sm(Co{sub 0.68}Fe{sub 0.2}Cu{sub 0.1}Zr{sub 0.02}){sub 7.5} alloy after isochronal heat treatments have been studied by using x-ray diffraction, transmission electron microscopy, three-dimensional atom probe (3DAP), and magnetometry. The as-spun ribbons had a single phase with the Cu{sub 7}Tb structure. After being aged at 720 deg. C, the single phase decomposed into two major phases: 2:17R and 1:5H, and one minor CoFeZr-rich phase. The formation of the Z-phase happened after the cellular structure, requiring a higher temperature than that for the cellular structure. The 3DAP analysis showed that Zr was depleted from the 2:17R and 1:5H phases by a half while the other elements remained almost unchanged when the aging temperature increased from 720 to 840 deg. C. In contrast to the sintered permanent magnets, Cu was enriched in the 1:5H phase with a much higher concentration (>40 at. %). The Cu enrichment also occurred at the boundary of the Z-phase. The coercivity achieved was H{sub c}=4.34 kOe following aging at 720 deg. C. The highest maximum energy product, (BH){sub max}, was 6.48 MG Oe after aging at 800 deg. C and the remanence to saturation magnetization ratio, M{sub r}/M{sub s}, was 0.69. This relatively low H{sub c} and high M{sub r}/M{sub s} ratio may be a consequence of the formation of a significant volume fraction of the CoFeZr-rich nanocrystalline phase.

• OSTI ID: 21185927
• Journal Information: Journal of Applied Physics, Vol. 104, Issue 10; Other Information: DOI: 10.1063/1.3021061; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AGING
COBALT ALLOYS
COERCIVE FORCE
COPPER ALLOYS
HEAT TREATMENTS
IRON ALLOYS
MAGNETIC PROPERTIES
MAGNETIZATION
MICROSTRUCTURE
NANOSTRUCTURES
PERMANENT MAGNETS
PHASE TRANSFORMATIONS
SAMARIUM ALLOYS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
TIME DEPENDENCE
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
ZIRCONIUM ALLOYS