Magnetic properties and microstructure of radially oriented Sm(Co,Fe,Cu,Zr)z ring magnets

Radially oriented Sm(Co,Fe,Cu,Zr)z ring magnets are prepared by powder metallurgy with appropriate magnetic field molding, sintering process and aging treatment. The results indicate that radially oriented Sm(Co,Fe,Cu,Zr)z ring magnets have obvious anisotropy of thermal expansion and sintering shrinkage, which easily lead to the splits and deformation of the ring magnets. So, slow heating, vacuum pre-sintering in sintering process and various quenching processes at different steps during quenching are adopted. The magnets have excellent magnetic properties: Br = 10.8 kGs, Hcj = 27.6 kOe, BHmax = 28.1 MGOe. Besides, there is a uniform magnetization field on the surface of the ring magnets. The average surface magnetization field (Bs―) is 1.502 kGs. The deviation from average (α) is only 4.2%. The microstructure of the magnets consists of a mixture of homogeneous cellular and lamella structures.