Impurity phases in Sm(CoFeCuZr)z magnets:: The role of Zr

Isotropic magnets were produced from cast alloys with composition Sm(CobalFe0.2Cu0.1Zrx)(8) (x = 0, 0.02, 0.04, 0.06 and 0.08). They were homogenized for 4h at 1175 degrees C and then quenched into water. An isothermal treatment for 7h at 820 degrees C was followed by a slow cooling (-1 degrees C/min) to 400 degrees C. For the Zr-free material (x = 0), we find mu H-0i(c),= 0.17T, while, for x = 0.02, the intrinsic coercivity has climbed to mu H-0i(c) > 2T and thereafter decreases with increasing Zr. Three main impurity phases were found in alloys with elevated Zr, and these phases can be identified with phases reported in the literature. The presence of the other phases could be related to the drop in H-i(c) for the high Zr alloys. (c) 2005 Elsevier B.V. All rights reserved.