Effect Of Rare Earth Oxides On Magnetic Properties And Mechanical Properties Of 2:17 Type Sm-Co Magnets

The 2:17 type Sm-Co permanent magnets play a very important role in high temperature fields such as defense and rail transit because of their good magnetic properties,excellent high temperature resistance,good temperature stability and corrosion resistance.However,2:17 type Sm-Co has poor plastic ductility because of its complex crystal structure,strong magnetocrystalline anisotropy,and powder metallurgy sintering process preparation,which would severely limit the further expansion of its application range.Therefore,improving the mechanical properties of 2:17 type Sm-Co rare earth permanent magnet materials has become an urgent problem to be solved.Because the magnetic properties and mechanical properties of the 2:17 type Sm-Co permanent magnets are mutually restricted,it is inevitable to significantly improve the mechanical properties at the expense of a part of the magnetic properties.At present,there is no effective way to improve the mechanical properties of 2:17type Sm-Co permanent magnets and maintain good magnetic properties at home and abroad.A large number of studies have shown that high-melting particles dispersed in the ceramic can effectively improve the toughness of the material.Considering that ceramics and2:17 type Sm-Co permanent magnets are the same brittle materials prepared by powder metallurgy.In this thesis,the effect of Y₂O₃/CeO₂ on magnetic properties and mechanical properties of 2:17 type Sm-Co magnets was studied by adding low cost and high melting poin rare earth oxide Y₂O₃ and CeO₂ in the high temperature resistant 2:17 type Sm-Co magnets.The main contents and results of this paper are as follows:1.In this paper,Sm(Co_balFe_0.09Cu_0.09Zr_0.03)_7.68.Y₂O₃ magnets were prepared by dual alloy and powder metallurgy processes.The effects of Y₂O₃ on the microstructure and magnetic properties of high temperature resistant 2:17 type Sm-Co magnets was investigated systematically.The results show that doped Y₂O₃ Sm-Co forms the 2:17 R phase in the solid solution state,Y₂O₃ promotes the orderly transformation of the 1:7H phase.Y element is mainly distributed in the oxide,and a small amount enters the main phase.With the increase of the amount of Y₂O₃ added,the Zr-rich 6:23 impure phase decreases and the Zr-rich lamellae phase density increases.The coercivity at room temperature of doped Y₂O₃ Sm-Co increases,the highest increase from 22.22 kOe to 28.44 kOe.The magnetic properties of magnets can reach the best when the Y₂O₃ doping amount is 0.5 wt.%at 550oC,the magnetic properties of magnets can reach the best:B_r=6.78 kGs,H_cj=6.27 kOe,?/?RT-550oC?=-0.05256%/oC and?/?RT-550oC?=-0.14702%/oC.When Y₂O₃ is doped into magnets,the Y elements are mainly combined with Sm,O and other elements in the form of oxides dispersed in the magnet.The high melting point oxide can absorb the energy and release the stress.The bending strength of the magnets is improved in the direction of h?c,b?c,l?c.The anisotropy of the flexural strength of the magnet with the Y₂O₃ addition amount of 3 wt.%is significantly reduced.The Vickers hardness indentation of the magnet was observed and it was found that the microcracks ended up at the oxide or around the peroxide.The low cost and high melting point rare earth oxides can effectively improve the mechanical properties of magnets,which would further expand the application range of the 2:17 type Sm-Co magnets.2.The addition of Y₂O₃ in an appropriate amount can not only improve the mechanical properties of the 2:17 type Sm-Co magnets,but also enhance the coercivity of the magnets at room temperature.The effect of CeO₂ on the microstructure and room temperature magnetic properties of high temperature 2:17 type Sm-Co magnets is further studied in this paper.Unlike the addition of Y₂O₃ Sm-Co magnets,in the solid solution state and aging state of the addition of CeO₂ Sm-Co,the Ce element is more evenly distributed in the magnet.With the increase of CeO₂ addition,the coercivity of magnets increases gradually,and t.the coercivity of magnets of exceeds 29.37 kOe when the amount of CeO₂ added is 3 wt.%.The coercivity of magnets can be improved obviously by adding rare earth oxide Y₂O₃/CeO₂,which would be a new technology to control coercivity of the 2:17 type Sm-Co magnets.