| The excellent magnetic of Nd-Fe-B has been widely applied into many high-tech fields since Nd-Fe-B came into being in 1980 s,such as new energy vehicles,medical treatment,wind power and so on.The development of Nd-Fe-B is the most rapid.The most widely used permanent magnet material is Nd-Fe-B,which has the largest potential development of market size.As a kind of basic functional materials,Nd-Fe-B is irreplaceable.But with the growing market demand,researchers have further need for Nd-Fe-B technical parameters.Not only it depends on the material itself,but also it has a close connection with the structure of the materials and the preparation process.Though researchers have done a lot of experimental studies on sintered Nd-Fe-B,the products are not competitive in the international market due to the high cost of the adding rare earth materials and the obsoleteness of the manufacturing facilites.So it has been a hot topic for scientific researchers both at home and abroad to study methods to reduce the cost and maximize the magnetic performance of Nd-Fe-B.The thesis prepares high coercive force sintered Nd-Fe-B magnet by combining the double-alloy powder mixed method with dysprosium(Dy)and cobalt(Co)nano-powder.The amount of Dy and Co nano-powder is allowed to be reduced while avoiding the slump of the boron remanence and magnetic energy products,thus the production cost is reduced.(Pr-Nd)31.5B0.98Co0.5Nb0.3Ga0.2Cu0.15Al0.1Febal+x%Dy sintered magnets are prepared on the industrial production lines.The thesis that uses scanning electron microscope(SEM)and other instruments analyzes many aspects,including the morphology,microstructure and composition,magnetic performance and mechanical performance of sintered Nd-Fe-B magnets.The results show that the coercivity of the magnet has been increased greatly with the increasing mass fraction of Dy element,while the remanence and maximum energy product has been decreased slightly.The coercivity that has been increased by 1.2% reaches the maximum value of 15.23 KOe when x is 1.6%.The remanence has been decreased by 2.7%,and the maximum energy product has been decreased by3.4%.Vickers hardness value is 522.01 HV,which has been decreased by 4%.The coercivity that has been increased by 5.4% reaches 14.29 KOe when x is 0.8wt%.The remanence has been decreased by1.3%,and the maximum energy product has been decreased by 1.5%.Vickers hardness value is583.47 HV,which has been increased by 7.1%.At this time,the comprehensive magnetic performance is optimal.(Pr-Nd)31.5-xB0.98CoxNb0.3Ga0.2Cu0.15Al0.1Febal sintered magnets are prepared on the industrial production lines.The thesis analyzes the relationships among the microstructure,magnetic performance,mechanical performance,temperature stability and Co addition.The results show that adding a certain amount of Co can effectively inhibit the formation of the ingot in ?-Fe.In the meanwhile,it forms intergranular phase to improve the coercivity,which is helpful to weaken the Nd-Fe-B intergranular exchange coupling effects.The coercivity,the remanence and the maximum energy product of the magnet increase firstly and then decrease as the mass fraction of Co element increases.The coercivity has been increased from 13.56 KOe to 14.44 KOe when x is 0.8.The remanence has been increased from 14.29 KGs to 14.35 KGs,and the maximum energy product has been increased from 49.32 MGOe to 49.55 MGOe.But magnetic performance has been decreased slightly when Co element is added to 1.2.So the comprehensive magnetic performance is optimal when x is 0.8. |
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