The ternary system Sm-Co-Zr isoplethic section at Co=89at.%

A knowledge of solid-liquid equilibria is necessary to optimise sintering temperature in industrial Sm2Co17-type magnets. A single-phase state is reported as precursor of the cellular microstructure of the Sm2Co17 permanent magnets. The formation of this phase at high temperature seems for a large part to be governed by Zr addition. In order to understand the behaviour of 2:17-type magnets, phase relationships have been investigated in the Co-rich field of the Sm-Co-Zr system. The 1150 degrees C isothermal section has been reinvestigated. A two-phase region was observed involving hexagonal and rhombohedral Sm2Co17. An isoplethic section has been drawn for temperatures between 1150 degrees C and the melting points of the alloy with Co=89 at.%, (Sm + Zr) = 11 at.%. Two four-phase equilibria have been observed. A tentative polythermal representation of the Sm-Co-Zr system in the Co-rich field has been drawn.