Phase Diagrams of Fe–Nd–B and Related Systems for Optimisation of Hard Magnetic Properties

Abstract

Permanent magnets based on Fe–Nd–B show high magnetisation and high coercivity at room temperature but unfavourable properties at higher temperatures. This behaviour has to be improved. The hard magnetic properties are limited by nucleation of severed domains, therefore the surfaces and interfaces of the grains constituting the material are the controlling factor. For any optimisation a detailed knowledge of the phase relations and microstructure development is needed. The parameters varied were: gross composition plus additives, the liquid phase sintering process parameters, and the following heat treatment. Phase relations and listed parameters in the systems Fe–Nd–B, Fe–Dy(Tb)–B, Fe–Nd–Al, Fe–Nd–C, and Fe–Nd–Dy(Tb)–B were investigated. PM/0589