Microstructure Characteristics of 2:17 SmCo Commercial Magnets With Different Coercivities

The correlation between microstructure and magnetic properties of 2:17 SmCo commercial magnets 32 H and 32 L is studied. The 32 H magnet with high coercivity has an excellent ( $00l$ ) orientation texture, and its magnetic properties are (BH) $_{\mathrm {max}}= 29.47$ MGOe, $B_{\mathrm {r}} = 11.20$ kG, and $H_{\mathrm {cj}} = 29.45$ kOe. The magnetic properties of the 32 L magnet with low coercivity are (BH) $_{\mathrm {max}}= 29.28$ MGOe, $B_{\mathrm {r}} = 11.40$ kG, and $H_{\mathrm {cj}} = 9.829$ kOe. The electron probe microanalysis results show that a Cu-lean grain boundary region is obvious in the 32 H magnet, which affects the squareness of the demagnetization curve. The transmission electron microscope result shows that the cell size and cell boundary thickness of high and low coercivity magnets are 129.32 and 9.83, and 90.94 and 7.87 nm, respectively. But the cell structure of the 32 H magnet is more complete and clearer than that of the 32 L magnet. The difference of the Cu concentration between the cell boundary phase and cell phase in the 32 H magnet is bigger than that of the 32 L magnet, which is really responsible for the high coercivity.