晶界扩散Dy–Al–Ga对钕铁硼磁体的磁性能和微观组织的影响
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摘要
通过晶界扩散Dy_(70)Al_(10)Ga_(20)合金研究了烧结Nd–Fe–B磁体的磁性能和热稳定性能.用NIM-500C高温永磁测量仪和MLA650扫描电镜测出了磁体在扩散前后的磁性能和微观组织的变化.结果表明,在Dy_(70)Al_(10)Ga_(20)合金扩散热处理后,磁体矫顽力从原始的1 080.968 kA/m显著提升到1 671.600 kA/m,提升幅度约为55%,而剩磁下降很少.Dy、Al、Ga元素在晶界处扩散,很好地隔绝了磁交换作用,提升矫顽力.SEM图显示在扩散Dy_(70)Al_(10)Ga_(20)合金后,可以很明显地看到晶粒外延层有一层灰色的壳层包覆着主相晶粒,很好地起到了隔离晶粒的磁交换作用.XRD显示主相的峰普遍往右偏移,这归因于重稀土元素Dy进入晶粒外延层形成(Nd,Dy)_2Fe_(14)B核壳结构.Dy的原子半径比Nd小,导致峰往右移.
The magnetic properties and thermal stability of sintered Nd–Fe–B magnets were studied by grain boundary diffusing Dy_(70)Al_(10)Ga_(20)alloy.The changes of magnetic properties and microstructure of the magnets were measured by NIM-500 C and SEM.The results show that after Dy_(70)Al_(10)Ga_(20)alloy receiving therma diffusion treatment,its coercivity is enhanced significantly from 1 080.968 kA/m to 1 671.600 kA/m,a striking increment of 55%.And there is only a slight reduction in remanence.Dy,Al and Ga elements diffuse at the grain boundary,which effectively insulates magnetic exchange so that the coercivity of the alloy is well improved.It is obvious that after Dy_(70)Al_(10)Ga_(20)alloy is diffused,in the epitaxial layer of grains is a gray shel covering the main phase grains via SEM,which plays an active role in magnetic exchange to isolate the grains The peak of the main phase is generally shifted to the right via XRD observation,given the fact that the heavy rare earth element Dy enters the epitaxial layer of grains and forms the(Nd,Dy)core shell structure.The atomic radius of Dy is smaller than that of Nd,causing the peak to move to the right.
The magnetic properties and thermal stability of sintered Nd–Fe–B magnets were studied by grain boundary diffusing Dy_(70)Al_(10)Ga_(20)alloy.The changes of magnetic properties and microstructure of the magnets were measured by NIM-500 C and SEM.The results show that after Dy_(70)Al_(10)Ga_(20)alloy receiving therma diffusion treatment,its coercivity is enhanced significantly from 1 080.968 kA/m to 1 671.600 kA/m,a striking increment of 55%.And there is only a slight reduction in remanence.Dy,Al and Ga elements diffuse at the grain boundary,which effectively insulates magnetic exchange so that the coercivity of the alloy is well improved.It is obvious that after Dy_(70)Al_(10)Ga_(20)alloy is diffused,in the epitaxial layer of grains is a gray shel covering the main phase grains via SEM,which plays an active role in magnetic exchange to isolate the grains The peak of the main phase is generally shifted to the right via XRD observation,given the fact that the heavy rare earth element Dy enters the epitaxial layer of grains and forms the(Nd,Dy)core shell structure.The atomic radius of Dy is smaller than that of Nd,causing the peak to move to the right.
引文
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[3]李强.钕铁硼永磁材料市场状况与发展前景[J].有色金属科学与工程,2001,15(4):38-40.
[4]KOHASHI T,MOTAI K,NISHIUCHI T,et al.Magnetism in grainboundary phase of a NdFeB sintered magnet studied by spinpolarized scanning electron microscopy[J].Applied Physics Letters,2014,104(23):1-5.
[5]高峰.钕铁硼永磁材料的生产与应用现状[J].有色金属科学与工程,1996,9(3):36-37,42.
[6]WU Y Q,TANG W,KRAMER M J,et al.Correlation of the energy product with evolution of the nanostructure in the Y,Dy,Nd-(Fe,Co)-B magnetic alloys[J].Journal of Applied Physics,2009,105(7):2907.
[7]LI W F,OHKUBO T,HONO K,et al.The origin of coercivity decrease in fine grained Nd-Fe-B sintered magnets[J].Journal of Magnetism and Magnetic Materials,2009,321(8):1100-1105.
[8]CHUBB D L,PAL A M T,PATTON M O,et al.Rare earth doped high temperature ceramic selective emitters[J].Journal of the European Ceramic Society,1999,19(13/14):2551-2562.
[9]LOEWE K,BENKE D,KUBEL,et al.Grain boundary diffusion of different rare earth elements in Nd-Fe-B sintered magnets by experiment and FEM simulation[J].Acta Materialia,2017,124:421-429.
[10]K T H.PARK K,SAGAWA M.Effect of metal-coating and consecutive heat treatment on coercivity of thin Nd-Fe-B sintered magnets[C]//16th Int.Workshop on Rare-Earth Magnets and Their Applications Sendai,Japan,2000.
[11]H U S Q,PENG K,CHEN H.Influence of annealing temperature on the Dy diffusion process in NdFeB magnets[J].Journal of Magnet ism&Magnetic Materials,2017,426:340-346.
[12]LI D S,NISHIMOTO M,SUZUKI S,et al.Coercivity enhancement of Nd-Fe-B sintered magnets by grain boundary modification via reduction-diffusion process[C]//IOP Conference Series:Materials Science and Engineering,2009.
[13]TANG W,DENNIS K W,KRAMER M J,et al.Studies of sintered MRE-Fe-B magnets by DyF3addition or diffusion treatment(MRE=Nd+Y+Dy)[J].Journal of Applied Physics,2012,111(7):07A736.
[14]LIU W Q,CHANG C,YANG Y M,et al.Coercivity enhancement of sintered Nd-Fe-B magnets by grain boundary diffusion with DyH2nanoparticles[J].Journal of Magnetics,2013,18(4):400-404.
[15]LU K,BAO X,TANG M,et al.Influence of annealing on microstructural and magnetic properties of Nd-Fe-B magnets by grain boundary diffusion with Pr-Cu and Dy-Cu alloys[J].Journal of Magnetism and Magnetic Materials,2017,441:517-522.
[16]OONO,NAOKO,SAGAWA,et al.Production of thick highperformance sintered neodymium magnets by grain boundary diffusion treatment with dysprosium-nickel-aluminum alloys[J].Journal of Magnetism and Magnetic Materials,2011,323(3):297-300.
[17]阎阿儒,宋晓平,王笑天.添加Al、Mg、W、Mo对烧结Nd-Fe-B磁体磁性能与显微组织的影响[J].中国稀土学报,1998,16(1):13-17.
[18]泮敏翔,葛洪良,张朋越,等.Ga和Ti掺杂NdFeB永磁体矫顽力的研究[C]//中国功能材料及其应用学术会议,中国仪器仪表学会,中国金属学会,杭州,2010.
[19]JIN C,CHEN R,YIN W,et al.Magnetic properties and phase evolution of sintered Nd-Fe-B magnets with intergranular addition of Pr-Co alloys[J].Journal of Alloys and Compounds,2016,670:72-77.
[20]SUMIN K,DONG-SU K,HYUM-SOOK L,et al.Enhancing the coercivity of Nd-Fe-B sintered magnets by consecutive heat treatment induced formation of Tb-diffused microstructures[J].Journal of Alloys and Compounds,2019,780:574-580.