| The structure and stability of the alloy system SmCo_(5-x)Cu_x with X in the range 1 to 4, have been investigated at temperatures between 600℃ and 1000℃ by X-ray diffraction techniques, electron microprobe analysis, and metallographic methods. It is shown that lattice constants of specimens annealed at 800℃ after homogenization increase with increasing the copper concentration, but do not follow the Vegard`s law. In the temperature range higher than 600℃ (but below 1,100℃), annealed specimens are unstable and a new phase having the Sm₂Co_(17) structure primarily precipitate along grain boundaries in the matrix and secondarily in the interior of grains. Electron microprobe analysis has exposed that those phases are enriched in cobalt and poor in copper as compared with the matrix. The result show that the copper element lowers the eutectoid decomposition temperature of SmCo_5 bulk alloy in great extent to near 600℃, and the sufficient heat treatment may cause the eutectoid decomposition of SmCo_(3·5)Cu_(1·5) ternary alloys. They also show that change in coercive force of SmCo_(3·5)Cu_(1·5) alloy between 600℃ and 800℃ can account for pinning interaction between domain wall movement and Co-rich precipitation particle. |
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