Relationships in the Fe-Nd/Sm/Pr-B Phase Diagrams determined by Iron Crucible Reaction Analysis (ICRA)

摘要

As a result of the discovery of permanent magnets based on the phases SmCO_5, Sm_2 (Co,Fe,Cu,Zr)_17 and Nd_2Fe_14B, a large amount of effort has been expended on the determination of a range of rare-earth/transition metal phase diagrams. For the most part, these studies have been carried out using conventional methods such as differential thermal analysis. The present work introduces and additional tool Iron Crucible Reaction Analysis (ICRA) for establishing phase diagrams and the technique is based on analogies between the tie-lines in a phase diagram and the diffusion paths in diffusion couples. The couples are formed by the use of iron crucibles in which the rare-earth elements are melted. During annealing or slow cooling from the melt, intermetallic phases are formed between the rare-earth element rich liquid and the iron crucible. These phases have been identified by a combination of Kerr effect (and conventional) metallography combined with EDX and/or WDX on an SEM. From the results of these investigations, a correlation can be made between the occurrence of these phases and the appropriate phase diagram. This provides an efficient and effective tool for establishing the pahse relationship in a range of alloy systems.