| Nd-Fe-B-type permanent magnetic materials have been widely concerned for their excellent magnetic properties and low price.At present,the Nd-Fe-B permanent magnets with high coercivity are mainly prepared by sintering and hot deformation.In this paper,without adding heavy rare earth elements such as Dy or Tb,the Nd-Fe-B permanent magnets with high coercivity are prepared by melt-spinning,which provides a new way to develop the high performance permanent magnetsThe Nd-Fe-B-type ribbons were prepared by arc-melting and melt-spining,the influence of the Al-Cu-Fe alloy addition,melt-spinning speeds and crystallization process on the micro structure and magnetic properties of the ribbons are studied by means of X-ray diffractometer,vibrating sample magnetometer,electron microscope and other instruments The main experiments and results are as following:The content of Al-Cu-Fe alloy has a direct influence on the micro structure and magnetic properties of the ribbons with a norminal composition of Nd13.5Fe74.9C05.5B6.0+x%Al89.5Cu9.7Fe0.5(x=0,1,2,3,7).The addition of Al-Cu-Fe alloy refines the grain size of the ribbons and promotes the precipitation of grain boundary phases.With the addition of Al-Cu-Fe alloy,the magnetic properties of ribbons first increase and then decrease,and the x=1 ribbons,which consist of Nd2(Fe,M)14B,Fe3B,Al13(Fe,M)4,Al9(Co,M)2,Nd-rich and amorphous phase,have the best average magnetic properties,namely Hc=13.6±1.3 kOe,Mr=66.1±4.7 emu/g,M2T=107.4±5.2 emu/gThe ribbons of Nd13.5Fe74.9Co5.5B6.0+1 wt%Al89.5Cu9.7Fe0.8 were fabricated by different melt-spinning speeds.With the increasing of melt-spinning speeds from 10 m/s to 40 m/s,the phase composition of ribbons is unchanged,all ribbons consist of Nd2(Fe,M)14B,Fe3B,Al13(Fe,M)4,Al9(Co,M)2,Nd-rich and amorphous phase,the grain size decreases from about 500 nm to 150 nm and the content of amorphous phase increases gradually from 2.54%to 10.84%.The best magnetic properties are obtained in the ribbons melt-spun at a speed of 40 m/sCrystallization annealing treatment process influences the microstructure and magnetic properties of the ribbons of Nd13.5Fe74.9Co5.5B6.0+1 wt%Al89.5Cu9.7Fe0.8.With the increase of annealing temperature from 650℃ to 750℃ and the prolongation of holding time from 10 min to 30 min,the grain size of Nd2(Fe,M)14B increases.When the holding time is less than 30 min,the ribbons all consist of Nd2(Fe,M)14B,Fe3B,Al13(Fe,M)4,Al19(Co,M)2,Nd-rich and amorphous phase;but when the holding time is 30 min,a new phase CuAl2 precipitates in the ribbons.The ribbons annealed at 710℃ for 20 min obtains the best magnetic properties of Hc=23.4±2.4 kOe,Mr=89.0±2.7 emu/g,M2T=109.5±4.5 emu/g,Mr/M2T=0.81The Nd13.5Fe74.9Co5.5B6.0+2 wt%Al89.5Cu9.7Fe0.8 as-cast ingots and the ingots annealed at 600℃ for 24 h were compared as raw materials of the ribbons melt-spun at 40 m/s.It is found that the ribbons made from the as-cast ingots consist of Nd2(Fe,M)14B,Fe3B,Al13(Fe,M)4,Al9(Co,M)2,Nd-rich and amorphous phase,and there is one more a-Fe phase in the ribbons made from annealed ingots.The coercivity of the ribbons made from the annealed ingots decreases from 11.2±0.5 kOe of the ones made from the as-cast ingots to 9.3±0.7 kOe,while the remanence improves from 6.2±0.2 kGs to 8.5±0.3 kGs,and the maximum magnetic energy product increases from 9.12 MGOe to 15.06 MGOe. |
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