MECHANICALLY ALLOYED SM-CO MATERIALS

The preparation of SmCo5 magnets is based on a high-temperature heat treatment above 800-degrees-C followed by a rapid cooling to room temperature. By mechanical alloying and a subsequent heat treatment, it is possible for the first time to prepare hard magnetic SmCo5 powder at low temperatures. The process involves first the formation of an amorphous precursor during milling, which then is transformed to the 1:5 structure at temperatures above 500-degrees-C. The magnetically isotropic samples show a coercivity of 24 kA/cm and a remanence of 0.52 T. The process is also applicable to Sm2Co17. However, here the coercivity is less than 5 kA/cm and higher values require the formation of a precipitation-hardened microstructure. The stability of SmCo5 below 800-degrees-C questions the eutectoid decomposition into Sm2Co17 and Sm2Co7.