Enhanced hard-magnetic properties and thermal stability of nanocrystalline Ce-rich Ce-Fe-B alloys by combining La substitution and Si addition

Abstract

To balance the utilization of rare-earth resource, Ce and La have been proposed to be employed in RE2Fe14B-type magnetic materials to produce fully high abundance rare-earth magnets. In this work, the effects of La on the phase constitution, microstructure and magnetic properties of melt spun (Ce1-xLax)17Fe78B6 alloys and (Ce1-yLay)17Fe75Si3B6 alloys have been systematically investigated. La effectively inhibits the formation of CeFe2 phase and increases the volume fraction of 2:14:1 phase. The TEM results indicate that La prefers to enter into intergranular phase and form bulk aggregations. La-substitution improves the remanence Jr, the maximum energy product (BH)max, curie temperature Tc and thermal stability, but reduces the coercivity Hc. Si modified (Ce1-yLay)17Fe75Si3B6 alloys exhibit better demagnetization curve squareness and superior magnetic properties than (Ce1-xLax)17Fe78B6 alloys due to the refined microstructure. In addition, Si-doped alloys show better thermal stability due to the enhanced curie temperature Tc. The results indicate that higher La content can be employed in Si doped Ce-Fe-B-based alloys for improved properties. The best combination of magnetic properties with (BH)max = 6.5 MGOe, Hc = 336 kA/m, Jr = 0.60 T and coercivity coefficient |β|=0.324 %/℃ is obtained in (Ce0.6La0.4)17Fe75Si3B6 alloy. The current work suggests that Ce-La-Fe-B alloys are potential to fabricate the so-called ‘Gap Magnets’, however, the composition modification is also required in order to improve their performance.