Preparation of isotropic Sm_2Fe_(17)N_x magnetic powders and their bonded magnets

摘要

The isotropic Sm2Fe17Nx magnetic powders were prepared by Hydrogenation-Disproportion-Desorption-Recombination (HDDR) process. The phase and microstructure evolutionary process of Sm-Fe alloy during the solidification, homogenization, HDDR and nitration processes were investigated by means of XRD, SEM, EDX and AFM. The results show that the homogeneous Sm2Fe17 alloy was successfully obtained and the impurity phases and residual stress were well removed by heated at 1050 ℃ for 24 h. When heated at 800 ℃ for 1h in H2 of 0.1 MPa, the alloy turns into SmHx and α-Fe with plenty of nanocrystals. After vacuumized at 800 ℃ for 2 h the alloy recombines into Sm2Fe17 with a crystal grain size of about 85 nm. The lattice constant of the alloy increases and the expanding of the crystal cell reaches 6.28% after nitrified at 500 ℃ for 5 h. The magnetic property of isotropic bonded Sm2Fe17Nx magnets is Br=0.6704 T, Hcj=1015 kA·m-1, (BH)max=73.7 kJ·m-3 with a density of 6.04 g·cm-3.