Thermal Decomposition and Magnetic Behavior of Co5Sm

Co 5 Sm is observed to be unstable at 750°C on the basis of transmission electron microscopy studies of thermally aged alloys. The decomposition products observed are Co 17 Sm 2 ( r ) precipitates and crystallographic shear (CS) planes constituting a disordered Co 7 Sm 2 ‐type structure. The possible effects of these products on the magnetic properties of the Co 5 Sm matrix are discussed.