Microstructure And Magnetic Properties Of SmCo/Fe(Co)Nanocomposite Permanent Magnet Materials

Sm-Co based nanocomposite permanent magnetic materials have the merits of high theoretical magnetic energy products（up to 100 MGOe）,high Curie temperatures and low rare-earth content.They are potential new generation of high-performance permanent magnetic materials,which have broad applications in aerospace,high-speed trains,wind power and new energy vehicles.In nanocomposite permanent magnetic materials,a high soft magnetic phase content（≥20%）is necessary to achieve a higher magnetic energy product.However,when the content of the soft magnetic phase is high（≥20%）,the coercivity of the Sm-Co based nanocomposite permanent magnetic materials prepared by the existing method is low,which limits their practical applications.Therefore,this thesis focuses on SmCo/Fe（Co）nanocomposite magnets,and discusses the influence of hot deformation temperatures,Sm₆₈Ni₃₂and Sm₇₆Zn₂₄low-melting-point eutectic alloy doping on the structure and magnetic properties of the magnets,which provides a theoretical basis and experimental support for high-performance nanocomposite magnets.The effects of hot deformation temperatures on the microstructure and magnetic properties of SmCo/Fe（Co）nanocomposite magnets were studied.The research results show that when the hot deformation temperature increases from 600℃to 1000℃,the coercivity of the magnets increases from 1.5 k Oe to 5.0 k Oe,the saturation magnetization of the magnet increases first and then decreases,reaching the maximum value at 700℃,the remanence of the magnets shows a trend of"first increase,then decrease,and then increase".As the hot deformation temperature increases from600°C to 1000°C,the content of the Sm₂Co₁₇hard magnetic phase in the magnets continued to increase,and the content of the Fe Co soft magnetic phase continued to decrease,and during 800-1000°C,Fe_0.28Co_0.72phase appears in the magnets.The increased content of the Sm₂Co₁₇hard magnetic phase is the primary reason for the continuous improvement of the coercivity of the magnets.The effects of Sm₆₈Ni₃₂alloy doping on the microstructure and magnetic properties of SmCo/Fe（Co）nanocomposite magnets were clarified.In SmCo/Fe（Co）nanocomposite magnets,2.5 wt.%,5.0 wt.%,7.5 wt.%,and 10.0 wt.%Sm₆₈Ni₃₂low-melting-point eutectic alloys（Ni is a ferromagnetic element）were doped,respectively.The coercivity of the SmCo/Fe（Co）nanocomposite magnets reaches the maximum value（7.3 k Oe）when the doping content is 7.5 wt.%.For the magnets without Sm₆₈Ni₃₂alloy,the phase composition of the magnets are Sm₂Co₁₇phase and Fe Co phase.After doping Sm₆₈Ni₃₂alloy,the phase composition of the magnet is Sm₂Co₁₇phase,SmCo₅phase and Fe Co phase.The doping of Sm₆₈Ni₃₂alloy stabilizes the SmCo₅phase which has strong magnetocrystalline anisotropy,thereby improving the coercivity of the magnets.The effects of Sm₇₆Zn₂₄alloy doping on the microstructure and magnetic properties of SmCo/Fe（Co）nanocomposite magnets were revealed.The coercivity of SmCo/Fe（Co）nanocomposite magnets can also be improved by doping 2.5 wt.%,5.0wt.%,7.5 wt.%and 10.0 wt.%Sm₇₆Zn₂₄low-melting-point eutectic alloys（Zn is a diamagnetic element）,respectively.The coercivity of the magnets reaches the maximum value（8.3 k Oe）when the content of Sm₇₆Zn₂₄alloy is 7.5 wt.%.For the magnets without Sm₇₆Zn₂₄alloy,the phase composition of the magnets is Sm₂Co₁₇phase and Fe Co phase.With the increase of Sm₇₆Zn₂₄alloy content,the main phase of the hard magnetic phase in the composite magnets are successively Sm₂Co₁₇phase,SmCo₅phase and SmCo₃phase.The increased content of the SmCo₅phase with high magnetocrystalline anisotropy in the magnets is the primary reason for the improvement of coercivity.Compared with Sm₆₈Ni₃₂alloy doping,Sm₇₆Zn₂₄alloy doping is more effective in improving the coercivity of the magnets due to the effect of the diamagnetic Zn element.