| Sintered（NdFeB）is a kind of rare earth permanent magnetic material with high coercivity,high remanence and high magnetic energy,which has become one of the indispensable special materials in high-tech field.However,the inhomogeneous distribution of Nd-rich grain boundary phase results in its coercivity in sintered NdFeB in actual production being much lower than the theoretical limit value.In addition,there is a large electrochemical potential difference between the Nd-rich grain boundary phase and the main phase in sintered NdFeB,which will induce intergranular corrosion and reduce its chemical stability,resulting in the deterioration of its corrosion resistance.Grain boundary addition technology was one of the main methods to improve the magnetic properties and corrosion resistance of sintered NdFeB.It was widely used because of its wide application,low cost and small effect on the main phase.By adding Pr-Cu alloy through grain boundary,the microstructure of sintered NdFeB could be optimized,the electrochemical potential difference between the Nd-rich phase and the main phase could be improved,and the sintered NdFeB material with high coercivity and corrosion resistance could be obtained.In this thesis,Pr-Cu alloy nanometer powder was prepared by DC arc method and added to sintered NdFeB.The effects of Pr-Cu doping on the magnetic properties and corrosion resistance of sintered NdFeB were investigated.the main content is as follows:（1）The electronic structure and mechanical properties of PrCu2 alloy were investigated by theoretical simulation.The molecular orbital of Pr Cu2 is a hybrid of Pr-f atomic orbital and Cu-d atomic orbital;The mechanical properties show that Pr Cu2 has brittleness and anisotropy of elasticity.（2）The effects of pressure,argon-hydrogen ratio and arc current intensity on particle size and productivities of Pr-Cu alloy nano-powder were studied.Based on the orthogonal method,the optimal experimental conditions for the preparation of Pr-Cu alloy nano-powder were investigated.When the current intensity was 200 A,the ratio of argon to hydrogen was1:1,and the reaction chamber pressure was 40-45 Torr,the particle size distribution range of Pr-Cu alloy nano-powder was narrow（50-90 nm）,and the powder yield was the highest,which could reach 1.60-2.9 g/h.（3）The effect of alloy doping ratio on the magnetic properties and corrosion resistance of sintered NdFeB was studied,and the improvement mechanism was explored.The magnetic properties and corrosion resistance of sintered NdFeB were tested by adding grain boundaries of Pr-Cu alloy with different proportions（0～0.8 wt%）to NdFeB micropowder and sintering into blocks.The results show that when the proportion of Pr-Cu alloy is 0.6wt%,the coercivity of the magnet reaches 1080.5 KA/m,which is 12.6%higher than that without Pr-Cu alloy,and the remanence decreases by 9.1%from 1.24T to 1.13T.The corrosion current density of magnet decreases from 62.0 m A/cm2 to 22.0 m A/cm2.After 96hours of weightless corrosion,the mass loss of the magnet is 4.5 mg/cm2,only 26.5%of that without adding,and the corrosion resistance of the magnet is significantly improved. |
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