Effect of residual hydrogen on microstructure and magnetic properties of Sm(Co0.647Fe0.28Cu0.053Zr0.02)7.84 magnets

Abstract Magnetic properties and microstructure of Sm(Co 0.647 Fe 0.28 Cu 0.053 Zr 0.02 ) 7.84 magnets prepared by HD powder with different residual hydrogen content (25, 715, 1512 ppm) have been investigated. The squareness and coercivity increase from 0.56 to 0.63 and 24.03 to 26.37 kOe as the hydrogen content increased from 25 to 1512 ppm. TEM results show that similar cellular structure and lamellar structures are formed in these magnets. Due to superabundant vacancies induced by hydrogen, the average grain size of final magnets increases from 50.22 to 62.29 μm with the increase of hydrogen in HD powder. Larger grain size results in fewer grain boundary areas where no clear cellular structure formed. The kerr observation indicate that the reversal domain formed at the grain boundary areas is easier to grow up, while the reversal of in-grain domain shows much harder.