Research On Technical Processes And Magnetic Properties Of NdFeB Melt-spun Magnets

In recent decades, the market demand of bonded NdFeB magnets has grown notably because of high magnetic and mechanical performance and good machinability, thus ushering the result that the annual output of NdFeB powder is increasing remarkably. Restricted by the equipment conditions and patent qualification, inland powders have no consequence in market. So it's necessary for us to explore the effects and effecting mechanism of alloying component and processing parameters on magnetic properties and microstructure of NdFeB powders, and improve the magnetic properties of inland powders.NdFeB permanence powders have been prepared by melt spinning NdFeB alloy in Ar and subsequent crystallization at proper temperature for condign time. The effects of melt-spinning and crystallization processing parameters and alloying component on the performance of Nd-Fe-B powders have been investigated systematically by the methods of XRD, TEM, SEM, DSC, TMA and magnetic performance character.The results show that, raidly quenching speed has nearly no influence on magnetic properties of the powder annealed in Ar. Crystallization process has a decisive effect on the magnetic properties of alloys. For Nd₁₀(FeCoZr)_83.5B_6.5 alloy, the optimal parameters are as follows :the melt-spinning pressure at 0.4 × 10⁵Pa, the spinning speed at 17m/s, crystallization temperature at 700℃ and crystallization time for 20²5min.The research on alloying component shows that, the optimum fraction of Nd is 10.5at%;the optimum fraction of B is 6.5at%. As to Nd₁₀(FeZr)_83.5-xCo_xB_6.5 alloy, the optimum fraction of Co is 4.6at%. With substituting Co for Fe atom, ferrite-magnetic exchange effect is enhanced and Curie temperature of magnets is increased.It can be attribute to some Zr atoms enter the Nd₂Fe₁₄B lattice and replace positions of Nd atoms, that practical hard magnetic phase content increases and the coercivity is improved remarkably. With adulterating Zr to nanocomposite Nd₂Fe₁₄B/α-Fe alloys, Nd₂Fe₁₄B and a-Fe phases deposit simultaneously, precipitation growing of a-Fe phase is delayed, then the grains are refined, that resultsin enhancement of exchange coupling between the 2:14:1 phase and a-Fe phase.In this paper, the optimal NdFeB powder can be obtained through the following alloys: Nd10.5Feg0B6.5Zr3 alloy with magnetic properties of 2?r = 8.22kGs, flc = 10.69kOe, fB//;wax=13.52MGOe and Nd^Feye^Be.sZrs.oCo^ alloy with magnetic properties of 5r=8.42KGs, ,#c=9.13KOe, (B//Jmac=13.98MGOe.