Permanent magnet alloys based on Sm2Co17; phase evolution in the quinary system Sm-Zr-FeCo-Cu

Abstract In the five-component permanent magnets based on Sm2Co17 the formation of the familiar microstructural features (2:17 cell, 1: 5 cell wall, and 1: 3 lamellae) are elucidated with the help of recent and past information on the phase equilibria and crystal structures. Contrary to Zr-free alloys, in which the 1: 5 cell-wall phase can form directly, the quinary alloys, to attain peak magnetic coercivity, undergo a transformation within the cell walls from undesirable 2: 7 + 5: 19 to high-anisotropy 1: 5. A dramatic increase in the Cu content of the cell wall accompanies this transformation.