| 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. |
PDF Full Text Request