22 KB126 KB21 KB199219991999Kobe, SpomenkaMcGuiness, Paul J.Žužek Rožman, Kristinaletnik:335 straništevilka:6str. 467-471ISSN:1318-0010COBISSID:204458URN:URN:NBN:SI:doc-Q3TS9KY9enInštitut za kovinske materiale in tehnologijeŽelezarna JeseniceŽelezarna RavneŽelezarna ŠtoreKovine zlitine tehnologijekoercitivnostmagnetne lastnostiprahovisamarijtantalzlitineželezoProcessing Sm-Fe(Ta)-N hard magnetic materials| Procesiranje trdih magnetov na osnovi Sm-Fe(Ta)-N|SmFe based alloys interstitially modified with nitrogen are potential candidates for high energy permanent magnets. >In order to obtain the optimum properties a thorough understanding of the starting material and processing parameters is required. The microstructures of two cast alloys of composition ?$Sm_{13,8}Fe_{82,2}Ta_{4,0}$? and ?$Sm_{13,7}Fe_{86,3}$? were carefully examined with a SEM equpped with EDX and the exact stoiciometries of the phases were determined. The SmFeTa material was found to contain significant amounts of ?$TaFe_2$?, as well as the ?$Sm_2Fe_{17}$?, ?$SmFe_2$?, ?$SmFe_3$? phases observed in the SmFe material but without the ?$\alpha$?-iron dendrites which are characteristic of the latter material. Hydrogen absorption-desorption studies carried out on both materials have demonstrated the increased resistance to decomposition of the ?$Sm_2Fe_{17}$? material, requiring an additional 150°C for the reaction to go to completition. The optimum conditions necessary to provide the highest coercivities using the conventional HDDR process combined with pre-milling were investigated. The coercivities obtained afted using the HDDR process and subsequent nitriding without any pre-milling were 680 kA/m for the SmFeTaN and 360 kA/m for the SmFeN samples. Significantly higher coercivities of 1000 kA/m for SmFeN were achieved by reducing the particle size with millin prior to the HDDR process. The better coercivities obtained with the Ta containing sample were found to be due to the presence of a much smaller amount of ?$\alpha$?Fe. The milling prior to the HDDR treatment improves the coercivity because of the small particle size, which prevents the grains going too large,with their consequent very negative effect on the coercivityZlitine na osnovi sistema Sm-Fe, intersticijsko modificirane z dušikom, imajo velik potencial kot trajni magnetni materiali. Optimalne magnetne lastnosti lahko dosežemo s pravilno obdelavo zlitine, ki pa temelji na poznavanju materiala. Primerjali smo zlitini sestave ?$Sm_{13,8}Fe_{82,2}Ta_{4,0}$? in ?$Sm_{13,7}Fe_{86,3}$?. Fazno sestavo smo preučevali z elektronsko vrstično mikroskopijo in EDX analizo. SmFeTa zlitina vsebuje ?$TaFe_2$? fazo, poleg nje pa tudi ?$Sm_2Fe_{17}$?, ?$SmFe_2$?, ?$SmFe_3$? faze, ki so prisotne tudi v SmFe zlitini z izjemo, da SmFe zlitina namesto ?$TaFe_2$? vsebuje dendritsko ?$\alpha$?Fe. Študirali smo procese absorbcije vodidka. Ugotovili smo, da Ta stabilizira ?$Sm_2Fe_{17}$? fazo, saj je bila temperaatura razpada te faze za 150°C višja od temperature, pri kateri je razpadla ?$Sm_2Fe_{17}$? faza iz binarne zlitine. Poiskali smo optimalne pogoje postopka HDDR, ki so nam dali najboljše rezultate na področju magnetnih lastnosti. Koercitivnosti prahov dobljenih po tem postopku in nadaljnjem nitriranju, so 680 kA/m za ?$Sm_{13,8Fe_{82,2}Ta_{4,0}N_x$? in 360 kA/m za ?$Sm_{13,8}Fe_{86,3}N_x$?. Občutno višje koercitivnosti smo dosegli z mletjem materiala, ki smo ga izvedli pred postopkom HDDR, t.j. 1275 kA/m za ?$Sm_{13,8}Fe_{82,2}Ta_{4,0}N_x$? in 1000 kA/m za ?$Sm_{13,8}Fe_{86,3}N_x$?. Razliko v viški koercitivnosti sestave s Ta, ge pripisati manjši vsebnosti ?$\alpha$?-Fe. Višje koercitivnosti pred mletega materiala pa dejstvu, da v majhnih delcih rast velikih zrn, ki imajo negativen vpliv na koercitivnost, nimožnaTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije