Study On Microstructure And Magnetic Properties Of (SmCo,NdFeB)/α-Fe(Co) Nanocomposite Permanent Magnets

Nanocomposite magnets have attracted wide attention from magnetic researchers due to their large theoretical energy product.The common nanocomposite magnets such as SmCo/FeCo or Nd₂Fe₁₄B/α-Fe contain single hard magnetic phase.However,compared to the single-phase magnet,the hybrid structure composed of two hard magnetic phases exhibits more excellent magnetic properties.In this dissertation,we use high-energy ball milling and high pressure thermal compression to prepare（SmCo,NdFeB）/α-Fe（Co）nanocomposite magnet.This dissertation mainly carried out the following work to conduct research:Mixing the SmCo/FeCo powders and NdFeB ribbon uses three different mixing methods（ball milling and grinding;separately ball milling;and jointly ball milling）.This dissertation is to study the effect of different mixing methods,NdFeB composition and content on the magnetic properties and microstructure of the nanocomposite magnets.The best mixing processes is making the SmCo/FeCo powders and NdFeB powders by high-energy ball milling,and then the two powders were ground and mixed uniformly.Prepared samples using this method have the best magnetic properties and microstructure.When the Nd₉Fe_83.2Ti₀.₈Nb₁B₆ content is 50 wt%,the cold-pressed blocks anneal at 700℃for 10 minutes obtaining the best magnetic properties:（BH）_max=9.4 MGOe,H_c=5 kOe,B_r=8.4kG,M_s=11.5 kG.The prepared cold-pressed blocks are subjected to high pressure thermal compression by Gleeble 3800 machine.To Study the effect of deformation temperature and Nd₉Fe_83.2Ti₀.₈Nb₁B₆ content on the magnetic properties and microstructure of the nanocomposite magnets.The results show that the anisotropy increases with the increase of the deformation temperature.When the temperature is 800℃,the anisotropy is the strongest.The I_（002）/I_（111）of SmCo₇ phase is 92%.And there is not obvious texture found in the Nd₂Fe₁₄B phase.The energy product of the nanocomposite magnet increases first,and then decreases again with the increase of the Nd₉Fe_83.2Ti_0.8Nb₁B₆ content.When the Nd₉Fe_83.2Ti_0.8Nb₁B₆ content is 30wt%,the best magnetic properties are obtained:（BH）_max=22.5 MGOe,H_c=4.4 kOe,B_r=11.7 kG,M_s=13.3 kG.The coercivity temperature coefficient is-0.24%/℃,and the temperature stability is better than that of the sintered NdFeB magnet.