A representation of the SmCoZrCuFe quinary system: a tool for optimisation of [formula omitted] permanent magnets

Abstract

In order to optimise the elaboration process of Sm 2Co 17 type magnets, the boundary of the single-phase domain at 1150°C and of the two-phase domain involving the 1 5 and the 2 17 at 850°C must be known. The knowledge of solid-liquid equilibria is also needed in order to avoid formation of other phases during sintering. It was then necessary to investigate phase equilibria in the SmCoZrCuFe system. However, since the variability of a such system under isobaric and isothermal conditions is four, the classic graphical representation can not be used. The presented part of the work concerns the region of interest near 1150°C. A specific approach of the quinary system is developed. It starts from the SmCo binary system, then the SmCoZr ternary system has been investigated: 1150°C isothermal section has been drawn for high Co contents and special attention has been paid to in the structural modification induced by Zr addition. Based on 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 concentration of 4 at.%. Finally a representation of the 1150°C single-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 the domain coupled with a three-dimensional one is applied. This representation makes possible to predict if a quinary alloy is single-phased at 1150°C or not. Magnetic behaviour of alloys is shown. This easy to read, easy to use representation appears a good tool to optimise the 2 17 -type permanent magnets.