Melt-spun precipitation hardened Sm(Co, Fe, Cu, Zr)z magnets

The effects of alloy composition and the temperature range of cooling regime on microstructure and magnetic properties of melt-spun Sm(Co0.74Fe0.1Cu0.12Zr0.04)7.5 (Cu/Zr-rich) and Sm(Co0.75Fe0.15Cu0.08Zr0.02)7.6 (Cu/Zr-poor) magnets were investigated. A very high coercivity of 2.8 T was obtained by applying a simple aging procedure to the as-spun Sm(Co0.74Fe0.1Cu0.12Zr0.04)7.5 ribbons, which is much higher than that of Sm(Co0.75Fe0.15Cu0.08Zr0.02)7.6 one. Transmission electron microscopy (TEM) shows that an uniform cellular and lamellar structure was observed in the annealed Sm(Co0.74Fe0.1Cu0.12Zr0.04)7.5 ribbons, which results from the single-phase TbCu7 type matrix in the as-spun ribbons, in contrast to a mixture of 2:17 and 1:7-type Sm–Co phases in the as-spun Sm(Co0.75Fe0.15Cu0.08Zr0.02)7.6 ribbons. High temperature measurements revealed that the temperature stability of the coercivity of Sm(Co0.74Fe0.1Cu0.12Zr0.04)7.5 ribbons is very sensitive to the temperature range of the cooling regime and the lower the quenching temperature, the more negative the temperature coefficient. A coercivity of 0.53 T at 500 °C was obtained in the sample quenched at 600 °C. Ribbons prepared by this simple processing route based on melt-spinning, in contrast to the conventional time consuming and intricate aging program, have a strong potential for a more economic preparation of bonded magnets in the future.