THE TERNARY-SYSTEM SM-CO-ZR ISOPLETHIC SECTIONS AT CO=87 AND 85 AT-PERCENT

The knowledge of solid-liquid equilibria is necessary to optimise sint ering temperature in industrial Sm2Co17 type magnets. A single-phase s tate is reported as precursor of the cellular microstructure of the Sm 2Co17 permanent magnets. The formation of this phase at high temperatu re seems, for a large part, to be governed by Zr addition. In order to understand the behaviour of 2/17 type magnets, phase relationships ha ve been investigated in the Go-rich field of the Sm-Co-Zr system. An i soplethic section with 89 at% Co has been presented already in a previ ous study. In the present paper, we have investigated the 1150 degrees C isothermal section with lower Co content. Two isoplethic sections h ave been constructed for temperatures between 1150 degrees C and the m elting points of the alloys with 87 and 85 at% Co. Two four-phase equi libria have been observed. In the Go-rich range of the ternary Sm-Co-Z r system, a tentative projection of the univariant liquidus lines has been constructed.