The crystal structure, oxidation resistance, and magnetic properties of SmCo7− x Si x ( x =0, 0.4, 0.6, and 0.9) permanent magnetic alloys were investigated systematically. It is found that the addition of silicon in the as-cast SmCo7 ingot plays an important role in stabilizing TbCu7 phase and improving inherent oxidation resistance. For the bulk nanocrystalline SmCo7− x Si x magnets, the oxidation resistance remarkably enhances but the corresponding Curie temperature T c and maximum energy product (BH)max exhibit a decreasing trend with the increase in Si content x . For the typical SmCo6.4Si0.6 nanocrystalline magnet, its final mass gain was about 1.71 mg/cm2 after oxidation at 500 °C for 100 h, indicating the enhanced inherent oxidation resistance. Its T c and (BH)max were about 708 °C and 35.4 kJ/m3, respectively.
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