SKOTNICOVÁ Kateřina VSB - Technical University of Ostrava

Spoluautoři KOSHKID’KO, Iurii S., ČEGAN Tomáš, KURSA Miroslav, BURKHANOV G.S., KOLCHUGINA N.B., LUKIN A.A., DORMIDONTOV A.G., SITNOV V.V.

Nd-Fe-B permanent magnets are used in many fields of industry. One of problems of preparation of permanent magnets based on the Nd2Fe14B compound is related to the decrease in the content of nonmagnetic phases via the optimization of the rare-earth metals contents. The strip-casting technology allows one to decrease the content of rare-earth metals in Nd-Fe-B permanent magnets and optimize their phase composition. The use powder mixtures, which consists of strip-casting (Nd,Pr)-Fe-B alloy and DyH2 hydride, allows the high-coercivity magnets to be prepared. The stability of the reached high magnetic characteristics in the course of both low- and high-temperature heat treatments was shown to be related to the evolution grain structure of the magnets. The microstructure and chemical composition of the permanent magnets was investigated using the high resolution field emission gun-scanning electron microscope QUANTA 450 FEG equipped with EDX microprobe. The studies of their microstructure have demonstrated annealing-induced changes in the thickness and continuity of (Nd,Pr,Dy)2Fe14B-phase grain boundaries and the shape of triple junctions of the grains. The microanalysis of triple junctions has revealed the presence of various (Nd,Pr,Dy)-O oxides such as (Nd,Pr,Dy)O, (Nd,Pr,Dy)2O3 and (Nd,Pr,Dy)O2. Studies of the microhardness of grains and triple junctions showed variations in values, which demonstrate correlations with the heat treatment conditions. The investigations performed allow us to conclude the effect of the heat treatment of the principal structural and magnetic characteristics of the permanent magnets.

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