Effect of the variation in Sm/Cu/Zr content on phase stability of an Sm(Co, Fe, Cu, Zr)7.4 permanent magnet alloy

T. S. Chin, W. C. Chang, R. T. Chang, M. P. Hung, H. T. Lee

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The effect of composition variation on the phase stability of an Sm(Co, Fe, Cu, Zr)7.4 system was studied to provide information on interpreting phase changes after partitioning of composition in the heat treatment of this alloy. Three quasi-binary phase diagrams were obtained by X-ray diffractometry, differential thermal analysis, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The major phase of all the alloys studied is either the 2:17H or 2:17R phase. However, additional phases appear as a result of compositional variations. (1) For the alloy system (Cu, Zr)-(11.9at%Sm-60.0Co-18.9Fe), fixing Cu+Zr = 9.2 at%, higher Zr facilitates the precipitation of a 2:7 phase, which is richer in both Sm and Zr. Zr also extends the homogeneity range of the 2:17 phase. To the Zr-lean end of this system the 1:5 phase appears. (2) For the alloy system Sm - (Co, Fe, Cu, Zr) with fixed Co/Fe/Cu/Zr ratio, higher Sm stabilizes the 2:7 phase, while to the Sm-lean end a Co-Fe phase with alpha Co structure precipitates. (3) For the system (Co, Fe) - (11.9 Sm-7.S Cu-l.7 Zr), fixing Co+Fe = 78.9 at%, the phase remains 2:17 unchanged for whatever variation in Co/Fe ratios. Zonal and grain boudary phases in a heat treated Sm(Co, Fe, Cu, Zr)7.4 alloy are depictable according to these phase diagrams.

Original languageEnglish
Pages (from-to)3782-3784
Number of pages3
JournalIEEE Transactions on Magnetics
Issue number5
Publication statusPublished - 1989 Sep

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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