The Effect Of Cu-doping On Magnetic Properties Of (Nd_1-yCe_y)_2.4Fe₁₄B Ribbons

NdFeB rare earth permanent magnet,which has very excellent magnetic properties,becomes the most widely used permanent magnetic materials in the world.However,with the increasing demand of NdFeB permanent magnet and the rising prices of raw material,the manufacturing cost of permanent magnetic materials has been significantly increased.Therefore,it is crucial to design and synthesis a novel permanent magnetic material with reliable performance and low cost.An effective method to reduce costs is replacing Nd element in the NdFeB permanent magnet by rare earth element Ce,which is rich in reserves but low in utilization.However,this substitution decreases the magnet crystalline anisotropy field thereby the performance of the magnet.For instance,the magnet of crystalline anisotropy field of Nd₂Fe₁₄B is 73 kOe,which is almost three times larger than that of Ce₂Fe₁₄B?26 kOe?.It is well known that the coercivity of permanent magnet materials can be well improved by doping of Cu element.In this sense,the thesis studied the effects of Cu-dopingon magnetic properties of(Nd_1-yCe_y)_2.4Fe₁₄B?y=0.2,0.5?alloy ribbons,and main innovations and achievements are as follows:?1?From the XRD and DSC patterns of(Nd_0.8Ce_0.2)_2.4Fei₄BCu_x?x=0,0.1,0.2,0.4,0.5?alloy ribbons,we can find that the ribbons with Cu doping concentration of 0.1 has characteristics of amorphous phase.A peak waist can be observed on the hysteresis loops of the ribbons due to the exchange coupling of the amorphous soft phase and the main phase.After annealed at 650? for 5 to 15 min,the grain size grow up at a certain degree and the a-Fe phase may occur in the ribbons.The magnetic properties of Cu-doped ribbons can keep stability after different annealing treatment times.In contrast,the samples without Cu doping are sensitive to annealing treatment time,as theirs squareness and magnetic properties has been improved after annealed for 5 min.With the increase of Cu doping concentration,the coercivity?Hcj?and remanence?Br?increases first and then decreased.After annealed with different times,the coercivity?Hcj?and remanence?Br?of the ribbons with a small amount of Cu doping increases,especially when the Cu concentration is 0.1 and 0.2.It indicates that a small amount of Cu element doping can improve the magnetic properties of the(Nd_0.8Ce_0.2)_2.4Fe₁₄BCu_x ribbons.?2?The properties of permanent magnet alloy ribbons are sensitive to their structures.The magnetic properties of the stripscan were affected by homogenization annealing treatment of the ingots.Our studies show that the amorphous soft magnetic phase for the alloy ribbons with Cu doping concentration of 0 and 0.3 would disappear if we anneal treated the ingot,and the characteristic of the peak waist arising from the soft magnetic and hard magnetic phases would eliminated.However,we compared all the ribbons without soft magnetic phase,the sample with Cu doping concentration of 0.1 still have the most excellent permanent magnetic properties,especially for the high Hcj,indicating the modification effect of Cu doping.?3?In the case of high Ce concentration,the properties of as-spun ribbons for(Nd_0.5Ce_0.5)_2.4Fe₁₄BCu_x?x=0,0.1,0.2,0.3,0.4,0.5?decrease with the increase of Cu concentration.After annealed at 650? for 5 min,the magnetic properties of samples without Cu doping are significantly deteriorated,while the ribbons with Cu doping concentration of 0.1 exhibit the optimal magnetic properties,as it has the highest coercivity,remanence and maximum energy product.