Production of Sm2Co17 Type Permanent Magnet Materials by the Reduction-Diffusion Process.

The Reduction-Diffusion (R-D) process was applied to the production of Sm2Co17 type rare earth permanent magnet materials with composition Sm (Co0.67Fe0.22Cu0.10Zr0.02) 7.2. The main objective of this study was the attainment of the specified composition in the final alloy product. For this objective, copper powder was excluded from starting materials and added after the R-D reaction, zirconium was added in the form of zirconia, and an aqueous ammonium chloride solution was used to leach out the remainder of metallic calcium and calcium oxide, the latter being formed during the reduction stage of the R-D process. The following were also examined; the amount of metallic calcium as a reductant, the grain size of cobalt powder, temperature and duration of the R-D reaction, homogenization condition of the alloy after the addition of copper powder, excess amounts of samarium oxide and zirconia among the starting materials, and so forth. The magnet alloy obtained in the present study contained a small amount of calcium and a little more oxygen than that prepared simply by melting metallic raw materials. Both of them, however, showed almost the same magnetic properties when treated by the identical step aging.