ALLOY FOR USE IN PREPARATION OF R-T-B-BASED SINTERED MAGNET AND PROCESS FOR PREPARING R-T-B-BASED SINTERED MAGNET

摘要

Processes for the preparation of a sintered alloy comprising R2Fe14B as a magnetic phase constituting a main phase include a binary alloy process wherein a main phase alloy having a lower R content than the above phase is mixed with a grain boundary phase alloy rich in R component and serving as a liquid phase in the sintering in order to prepare a mixture to be used as the starting material. The conventional main phase alloy has a structure comprising the R2Fe14B phase and, in addition, a large amount of an easily oxidizable lamella R-rich phase and a harmful dendrite alpha phase. On the other hand, the main phase alloy of the invention has a low dendrite alpha phase content and a low lamella R-rich phase and contains a lamella alpha Fe phase. This contributes to excellent oxidation resistance and improved properties of the magnet. The preparation of a sintered magnet by mixing the main phase alloy with the grain boundary phase alloy by the binary alloy method can reduce abnormal growth of crystal grains.