The Study On Microstructure And Magnetic Properties Of SmFeN Magnets Prepared By Low Temperature Hot Pressing Process

Permanent magnet material is the key material necessary for the healthy and steady development of various high-tech fields.Although the existing NdFeB rare earth permanent magnet materials have high magnetic properties and are widely used,NdFeB rare earth permanent magnet materials will consume a large number of Nd,Pr,Dy,Tb and other rare earth elements,resulting in the unbalanced use of rare earth strategic elements,and even the waste of rare earth elements.Therefore,the development of low rare earth or high abundance rare earth permanent magnet materials is a research focus in the field of rare earth permanent magnet materials.SmFeN permanent magnet material has the advantages of high Curie temperature,high cost performance,high magnetocrystal anisotropy and corrosion resistance,and has been widely concerned for a long time.However,the development and application of SmFeN permanent magnet materials are hindered due to its low coercivity and the difficulty in preparing full-density and high-performance block magnets by traditional sintering or thermal deformation.In this thesis,by controlling the ball grinding time to improve the coercivity of SmFeN.Using numerical simulation software to simulate the hot pressing process of SmFeN at different temperatures,through the equivalent stress and strain analysis of the internal uniformity of the magnet change law,to find the best hot pressing temperature and obtain the SmFeN magnet with the best performance.By using different hot pressing technology and the influence of different technology,temperature and pressure rate on hot pressing magnet is analyzed.Determine the best hot pressing technology,which will have certain reference significance for the preparation of high performance SmFeN magnet.The conclusions of this thesis are as follows:(1)The coercivity of SmFeN magnetic powder can be improved by optimizing the high energy ball milling process.When the ball milling time is 12 min,the coercivity reaches the peak value of 11 kOe.With the extension of ball milling time,the coercivity decreases and the magnetic anisotropy remains.Through the observation and analysis of the microstructure and XRD pattern,high-energy ball milling process can significantly reduce the grain size of the magnet,make the grain better dispersion,which is conducive to the increase of magnetic coercivity of the magnet.but the long ball milling time,SmFeN magnetic powder partial decomposition,magnetic properties of magnetic powder seriously reduced.(2)Based on Deform 3D software,the change of equivalent stress and equivalent strain of hot pressed magnets at different temperatures were studied.The results show that the equivalent strain distribution is most uniform when the hot pressing temperature is 400℃.However,in the process of hot pressing,the magnetic surface center is easy to interact with the mold to cause stress concentration.It should be adopt the method to avoid.(3)SmFeN block magnets with higher compacting and comprehensive magnetic properties can be obtained by hot pressing with copper bushing bound magnets.By optimizing the hot pressing process,the hot pressing SmFeN magnet was obtained.Finally,the bulk density is 6.58 g/cm~3,the coercive force is 4.00 kOe and the remanence is 3.149 kGs.