Phase transformation and magnetic properties of Sm(Co0.91-xFexCu0.07Zr0.02)z powders for bonded magnet applications

Structural and magnetic properties of Sm(Co0.91-xFexCu0.07Zr0.02)(8.0), where x = 0, 0.12, 0.21, 0.29, and 0.32, and Sm(Co0.64Fe0.28Cu0.06Zr0.02)(z), where z ranged from 6.9 to 8.6, have been systematically investigated by x-ray powder diffraction. It was found that most of these alloys exhibit a hexagonal Th2Ni17 structure with a space group P6(3)/mmc after an optimum solid solution treatment with rapid quench. The fully processed materials (after precipitation hardening) all exhibit a rhombohedral Th2Zn17 structure with a space group of R (3) over bar m as the primary phase. For Sm(Co0.91-xFexCu0.07Zr0.02)(8.0), the lattice parameters, a and c, and cell volume, V, increase slightly at first with increasing x, and then more sharply when x is increased above 0.28. The latter drastic increase in lattice parameters and cell volume results in a sharp decrease in the H-ci, H-c, and H-k values of fully processed materials. For Sm(Co0.64Fe0.28Cu0.06Zr0.02)(z), the lattice parameters, a and c, and cell volume increase slightly when z is varied from 6.8 to 7.8, then exhibit a drastic decrease when, is further increased beyond 8.0. A B-r of 11.3 kG, H-ci of 27 kOe, and BHmax of 30 MGOe have been obtained on Sm(Co0.63Fe0.28Cu0.07Zr0.02)(8.0) after a solid solution at 1160 degrees C and aging at 850 degrees C. (C) 1998 American Institute of Physics. [S0021-8979(98)15711-0].