| In order to show the connection between microstructure and magnetic properties, studies have been made of the effect of composition and aging treatment on the magnetic properties of the alloy system SmCo_5-SmCu_5. A number of ingots of the ternary composition SmCo_(5-x)Cu_x (x=1 to 4) were prepared by arc-melting under a protective atmosphere, resulting in a rapid freezing from the molten state. The samples were then annealed at various temperatures between 400℃ and 1000℃. The magnetic properties of these compounds were the highest in the vicinity of the composition SmCo_(3.5)Cu_(1.5) and SmCo_(3.0)Cu_(2.0). When specimens of the composition SmCo_(3.5) Cu_(1.5) annealed at 1000℃ and 400℃ were examined by optical microscope, X-ray diffraction, and electron-probe techniques, there were observed fine needle-shaped precipitates which may be responsible for the magnetic hardening of this compound. Their hexagonal cell constants (a=8.402A, c=12.172A) were obtained from FeKα powder diffraction data. The results indicate that precipitates occurring at the low temperature annealing are the same kind of phase as Sm₂CO_(17) precipitates at the high temperature annealing, and they appear to overage rapidly during the annealing between 400℃ and 600℃. Therefore, annealing at the high temperature over 600℃ does not lead to a further increase in the magnetic properties of SmCo_(5-x)Cu_x alloys. |
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