Microstructures of precipitation-hardened SmCo permanent magnets

The microstructural features of isothermally aged and step aged and isothermally aged Sm(Co, Cu ,Fe, Zr)7.4 alloys are examined using electron microscopy and x-ray microanalysis. The microstructure is seen to consist of a cellular morphology with twinned rhombohedral 2:17 phase cell interiors, 1:5 phase cell boundaries, and elongated thin platelets with a 1:3 structure. Upon prolonged aging, Zr preferentially goes into the 1:3 phase, Cu to both …