Microestrutural and magnetic properties characterization of PrFeCoB-based alloys and permanent HD sintered magnets

Abstract

The magnets were produced by powder metallurgy route, using powders obtained by hydrogenation-decrepitation method (HD). The compositions of the alloys were: Pr20FeBalB5Cu2 (33% wt.) and Pr14FebalCo16B6Nb0,1(AlSiCuGaGd)x (where x = 0,3 e 0,5) (67% wt.). The characterization of the alloys and the magnets produced have been carried out using backscattered electron microscopy (BEM), energy-dispersive X ray spectroscopy (EDXS), X ray diffraction (XRD), X ray fluorescence (XRF) and magnetic properties have been measured using a permeameter. The results revealed that the Fe-rich phase is prejudicial to magnetic properties and the improvement of the properties is due to the elimination of the Fe-rich phase by heat treatment (1343K for 20 hours). Therefore, the magnets produced by heat treated alloys presented a maximum energy product 50% higher when compared with the magnets produced by as-cast alloys. The magnet produced by Pr14FebalCo16B6Nb0,1(AlSiCuGaGd)0,5 heat treated alloy presented the best values for remanence (Br = 1.03 T), maximum energy product ((BH)máx = 201.6 KJ.m-3) and intrinsic coercivity (iHc = 716.2 KA.m-3).