Abstract
Sm-Co-Cu-Fe-Zr phase diagram near compositions of magnet alloys, that is, Sm-Co-7.0 at%Cu-22.0 at%Fe-(0, 1.4, 2.0 and 3.0 at%)Zr sections of the phase diagram were determined in the Sm content range from 6 to 16 at% above 1073 K, and effects of Zr on the phase transformation and magnetic properties of the magnet alloys were investigated. The results are summarized as follows:
(1) Addition of Zr by 1.4 or 2.0 at% expands the Sm solubility in 2/17 phase towards both richer and poorer side, and changes the crystal structure of 2/17 phase to TbCu7 and/or Th2Ni17 type structure(s) at high temperature. Addition of Zr by 3.0 at% expands (2/17+2/7) phase region, in which 2/17 phase has the TbCu7 and/or Th2Ni17 type structure(s).
(2) Sm(Co, Cu, Fe, Zr)z alloys possess high coercivity, when homogenized in 2/17 single phase with TbCu7 (Zr 1.4 and 2.0 at%) at high temperature and decomposed into 2/17 phase with Th2Zn17 type structure and 1/5 phase with CaCu5 type structure by aging treatment. The alloys which have this phase transformation shift the Sm content towards poorer Sm as the Zr content increased, and possess high coercivity in the above-mentioned Sm and Zr content range.
