The Study On Microstructure And Magnetic Properties Of Hot-deformed 1:12 Bulk Sm-Fe-Ti Nanocrystalline Permanent Magnets

With the intensification of global greenhouse effect,the society needs the development of green technology to reduce or avoid CO₂emissions and achieve the"double carbon"goal.Therefore,it is necessary to develop efficient and energy-saving generators and motors to achieve the goal of green,energy conservation and environmental protection.In order to achieve high efficiency and energy saving of generators and motors,high-performance permanent magnet materials are essential.Although there are NdFeB rare earth permanent magnet materials with excellent performance as the core material support of green technology,due to the low Curie temperature of NdFeB rare earth permanent magnet materials,it is difficult to meet the normal operation of generators and motors at the operating temperature of about 150℃.Based on this reality,it is necessary to develop a permanent magnetic material with high temperature magnetic properties superior to NdFeB magnets to meet the needs of various green technologies.The RFe₁₂（R is rare earth element,generally Sm）based compound with ThMn₁₂crystal structure is a permanent magnetic material with potential to meet the current green technology development because it contains the lowest rare earth element and has excellent intrinsic magnetic properties.But its phase instability and intrinsic coercivity（μ₀H_c）hinders the development and application of RFe₁₂permanent magnetic materials.Therefore,more research is needed for RFe₁₂rare earth permanent magnetic materials.In this thesis,SmFe₁₁Ti ribbons were prepared by melt rapid quenching technology,and the best samples were obtained by adjusting the process parameters.The preparation process of SmFe₁₁Ti at different temperatures was simulated by using numerical simulation software,providing guidance for subsequent hot deformation experiments.After that,SmFe₁₁Ti bulk magnets were prepared by hot deformation technology with strip as precursor,and the properties and microstructure of the bulk were tested.The best hot deformation process for preparing 1:12 type Sm-Fe-Ti permanent magnet was investigated.The conclusion is as follows:（1）The optimal preparation process of SmFe₁₁Ti strip was obtained by adjusting the process parameters.The melting temperature was 1200℃,the optimal copper roll speed was 20 m/s,the nozzle height from the copper roll was 1 mm,and the injection pressure difference was 0.05 MPa.The strip prepared under this condition has anisotropy,the coercive force can reach 5.251 k Oe,and the maximum magnetic energy product（BH）_maxis 6.179 MGOe.（2）Based on Deform 3D software,the hot deformation process of SmFe₁₁Ti magnet was simulated and analyzed.The results show that the magnets prepared by biaxial pressurization are more compact,and the distribution of equivalent strain in the magnets is the most uniform at 700℃..（3）SmFe₁₁Ti bulk magnet with high comprehensive magnetic properties was obtained by hot deformation of strip with process parameters of 1300℃melting temperature,20 m/s rotating speed of copper roll,1 mm nozzle height from copper roll,and 0.05 MPa jet pressure difference.By optimizing the hot deformation process,a hot deformed SmFe₁₁Ti bulk magnet with a maximum magnetic energy product（BH）max of 3.732 MGOe and a remanence of 8.102 k Gs was finally obtained.