Structure changes in Sm-Fe-B-Ti permanent magent materials induced by HDDR process

摘要

The HDDR (hydrogenation-disproportionation-desorption-recombination) process has been successfully used as an effective method for obtaining highly coercive rare-earth and transition metal magnets by changing originally coarse grained materials into those of fine grains (typical grain size: approx 0.3 mum). The HDDR process is completed by the disproportionation of the original compound to a rare-earth metal hydride and alpha-Fe grains by hydrogenation, and then their recombination to the original structure, but with fine grains, by the hydrogen desorption. Thus, understanding structural changes after the hydrogenation-disproportionation (HD) and the desorption-recombination (DR) processes are important to control the final structure, which strongly influences permanent magnetic properties.