Effect of Strip Casting on Microstructure and Magnetic Properties of 2:17 Type Sm-Co Sintered Magnets

The 2:17 type Sm-Co sintered magnets were made with strips and ingots, separately. The phase structure and microstructure of the cast alloys and their effects on magnetic properties of the magnets have been comparatively studied. X-ray diffraction analysis shows that the phase structure of strips and ingots both consist of TbCu₇-type phase with a little CaCu₅-type phase. Scanning electron microscopy research shows that the microstructure of strips is composed of dendritic crystal grains which are larger than 10 μm in cross section and less than 4 μm in the free side, whereas, the grain size of ingots is larger than 40 μm. Higher remanence and maximum magnetic energy product are observed in magnets made with ingots (IM) than that made with strips (SM), which is due to low grain alignment degree of the magnets made with strips. In order to increase the grain alignment degree of magnets made with strips, the powder particle size has been reduced. Fruitfully, the remanence and the maximum energy products gradually increase with decreasing the powder particle size.