Microstructural evolution of Sm(Co1−xCux)5 (0<x<0.5) alloys

Abstract Microstructural studies were performed in Sm(Co 1− x Cu x ) 5 alloys with x =0.0, 0.2, 0.3, 0.4 and 0.5. The coercivity increases with Cu content in the studied range of compositions, while the Curie temperature decreased. X-ray diffraction only showed the presence of the hexagonal CaCu 5 -type structure belonging to a Sm(Co,Cu) 5 phase in all the studied compositions. The solubility of excess Sm in the Sm(Co,Cu) 5 phase increases with Cu content. The x =0.3 sample showed needle-like coherent precipitates inside the matrix grains and platelet precipitates at grain boundaries. Both precipitates had a composition close to a Sm 2 (Co,Cu) 7 phase. The x =0.5 sample showed a different microstructure with regions which are thought to be the result of twinning. Evidence of heavy faulting was also found. The occurrence of a disordered CaCu 5 -type structure with Sm excess is discussed in terms of its possible magnetic significance in the observed pinning driven magnetization mechanism.