Influence Of Y Substitution On Permanent Magnetic Properties Of Nd-Fe-B Melt-Spun Ribbons

Since its discovery,NdFeB rare earth permanent magnetic materials have been widely used in electronic products,medical devices,automotive industry,energy transportation and other fields with its superior comprehensive magnetic properties.However,with the continuous innovation of technology,the requirements for the heat resistance of the magnets are also getting higher and higher.Therefore,a single Nd-Fe-B permanent magnet material no longer meets the market demand.With the production of neodymium iron boron and the consumption increases year by year,metal Nd which is a raw material and metals Tb and Dy which are commonly used additives are also being consumed at a faster rate,leading to an increase in the cost of materials year by year.Therefore,there is an urgent need to find other rare earth metals that can replace these scarce resources.While improving the heat resistance of NdFeB,the production cost of permanent magnets is reduced,so as to meet the market demand and realize the comprehensive balanced utilization of rare earth resources.Y₂Fe₁₄B has a positive temperature coefficient of coercivity over a certain temperature range,and the Curie temperature is slightly higher than neodymium iron boron at room temperature,indicating that Y can be used as an additive element to improve the heat resistance of neodymium iron boron through appropriate processes.The effect of yttrium on thermal stability and magnetic energy of Nd_12-xY_xFe₈₁B₆Nbi melt-spuns is systematically studied in this paper.The main research contents and results are as follows:?1?DSC analysis show that the crystallization peaks of melt-ribbons continue to shift to the right as the content of Y increases,suggesting that the substitution of Y make the amorphous more stable and conducive to the formation of amorphous.The results of XRD analysis of quenched samples show that except for a small amount of soft magnetic phase Fe₃B,all samples have a 2:14:1 hard magnetic phase,and the main phase diffraction peaks shift to the left as the amount of x increases,studies have shown that this is mainly due to the fact that the substitution of Y into the tetragonal main phase leads to a change in the lattice constant of the main phase of the matrix.?2?With the increase of Y content,the coercivities of melt-ribbons continuously decreases,this is due to the fact that Y entering the tetragonal phase,resulting in a decrease in the anisotropy field of the hard magnetic phase.However,the substitution of Y does not reduce the remanence.On the contrary,a certain amount of Y replaces the Nd element,resulting in an increase in remanence.In this paper,the best magnetic properties of Hcj=11.41kOe,?BH?_max=16.23MGOe are obtained when the amount of x is 1.0 in Y-containing samples.Compared to the initial alloys that do not contain Y element,the magnetic energy product increases by 8.2%,the Henkel curve shows that this is mainly attributed to the fact that the addition of Y promotes the exchange coupling of soft and hard magnetic phases between adjacent grains.The TEM images of the quenched samples show that the addition of a suitable amount of Y can refine the grain.When the amount of x is 1.0,the average grain size of the melt-ribbon changes from the initial 59.78 nm to 38.44 nm,and the morphology of Y-containing samples is more uniform.?3?When the bonded magnets with different Y contents are aged at 150? for 350h,the magnetic flux losses are changed.Among them,in the magnet without Y element,the magnetic flux loss is 2.739%after thermal demagnetization for 350h,while the substitution of 0.5at%and 1.0at%Y element for the Nd element in Nd-Fe-B,the magnetic flux loss of the bonded magnet is lower than the initial value,and the corresponding magnetic flux losses were 2.124%and 2.466%respectively,indicating that the addition of Y increased the time stability of the bonded magnets.?4?With the increase of Y contents,the temperature coefficients of bonded magnets decrease continuously,that is,the addition of Y improves the heat resistance of the magnets,the coercive force temperature coefficient ?changes from-0.3198%/??x=0?to-0.157%/??x=5.5?,the corresponding remanence temperature coefficient a changes from-0.40%/? to-0.32%/?.In this paper,the Y-Ce substitution in another system of?Nd,Ce,Y?₁₂Fe₈₁B₆Nb₁ is performed by vacuum melt-quenching.It is found that the addition of Y can form amorphous completely at a lower wheel speed of 18m/s,but when the Y element is not present,the resulting samples have a distinct diffraction peak,indicating that Y element can promote the formation of amorphous alloy.In the case of adding only Ce element,the temperature coefficient of the magnet cannot be reduced,that is,its thermal stability is not improved;the addition of Y element causes the temperature coefficient of the coercive force of the magnet to drop significantly,which can be beneficial to the heat resistance.