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

Microstructural studies were performed in Sm(Co1-xCux)(5) alloys with x=0.0 , 0.2, 0.3, 0.4 and 0.5. The coercivity increases with Cu content in the st udied range of compositions, while the Curie temperature decreased. X-ray d iffraction only showed the presence of the hexagonal CaCu5-type structure b elonging to a Sm(Co,Cu)(5) phase in all the studied compositions. The solub ility 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 gr ains 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 dif ferent microstructure with regions which are thought to be the result of tw inning. Evidence of heavy faulting was also found. The occurrence of a diso rdered CaCu5-type structure with Sm excess is discussed in terms of its pos sible magnetic significance in the observed pinning driven magnetization me chanism. (C) 1999 Published by Elsevier Science S.A.