Study On Magnetic Properties And Electrochemical Corrosion Properties Of Nd₂Fe₁₄B/?-Fe Nanocrystalline Composite Magnets

The Nd₂Fe₁₄B/?-Fe nanocomposite permanent magnet is composed of a high magnetocrystalline anisotropy Nd₂Fe₁₄B phase and a high saturation magnetization?-Fe phase at a nanometer scale by a grain-to-grain strong exchange coupling effect.The higher theoretical magnetic energy product is expected to develop into a new generation of rare earth permanent magnet materials.However,on the one hand,the actual prepared magnet does not reach the ideal microstructure,and the magnetic properties of the magnet are far from the theoretical value.On the other hand,there is a potential difference between the hard magnetic phase and the soft magnetic phase of the multiphase magnet,which easily forms a corrosive microbattery to destroy the magnet structure.The exchange coupling of nanocomposite permanent magnets mainly occurs at the interface.The structure and chemical properties of the interface have an important influence on the magnet.Therefore,the regulation of the interface structure has become a hot topic.In this paper,Nd₂Fe₁₄B/?-Fe nanocrystalline magnets were prepared by melt quenching technique.The effects of rapid quenching process and element addition on the magnetic properties and electrochemical corrosion properties of Nd₂Fe₁₄B/?-Fe permanent magnets were investigated.It is found that as the quenching speed increases from 13 m/s to 17 m/s,the grain size of the two phases is refined,the magnetic properties are improved,the corrosion current density is increased,the charge transfer resistance is decreased,and the corrosion resistance is deteriorated.However,at the 19 m/s quenching speed,the magnet has an interface amorphous phase,and at the same time optimizes the interface microstructure and chemical stability.The magnetic energy product increases to 20.9 MGOe,while the low corrosion current density 44.5?A/cm² and the large charge transfer resistance 425.1?·cm² make magnetic properties and electrochemical corrosion performance are simultaneously improved.It is found that the coercive force of the magnets is the domain wall pinning mechanism.As the Nb content increases,the grain size of the two phases decreases,and the interface amorphous phase content increases to 19%,so that the magnetic energy product increases first.The corrosion resistance increases.When the Nb content is 1 at.%,the comprehensive performance of the magnet is optimal:the magnetic energy product is22.9 MGOe,the corrosion current density is 34.2?A/cm²,and the charge transfer resistance is 316.2?·cm².