A REPRESENTATION OF THE SM-CO-ZR-CU-FE QUINARY SYSTEM - A TOOL FOR OPTIMIZATION OF 2 17 PERMANENT-MAGNETS/

In order to optimise the elaboration process of Sm2Co17 type magnets, the boundary of the single-phase domain at 1150 degrees C and of the t wo-phase domain involving the 1/5 and the 2/17 at 850 degrees C must b e known. The knowledge of solid-liquid equilibria is also needed in or der to avoid formation of other phases during sintering. It was then n ecessary to investigate phase equilibria in the Sm-Co-Zr-Cu-Fe system. However, since the variability of a such system under isobaric and is othermal conditions is four, the classic graphical representation can not be used. The presented part of the work concerns the region of int erest near 1150 degrees C. A specific approach of the quinary system i s developed. It starts from the Sm-Co binary system, then the Sm-Co-Zr ternary system has been investigated: 1150 degrees C isothermal secti on has been drawn for high Co contents and special attention has been paid to in the structural modification induced by Zr addition. Based o n our knowledge of the ternary system, the Sm-Co-Zr-Cu quaternary one has been studied; an isothermal section has been drawn for a Cu concen tration of 4 at.%. Finally a representation of the 1150 degrees C sing le-phase domain in the quinary system Sm-Co-Zr-Cu-Fe is proposed. For this purpose, a method consisting of a two-dimensional projection of t he domain coupled with a three-dimensional one is applied. This repres entation makes possible to predict if a quinary alloy is single-phased at 1150 degrees C or not. Magnetic behaviour of alloys is shown. This easy to read, easy to use representation appears a good tool to optim ise the 2/17-type permanent magnets. (C) 1997 Elsevier Science S.A.