Research On Microstructure And Properties Of Rare-Earth Permannent Magnetic Materials Under Irradiation/High Temperature

In this paper,Sm Co alloy and Nd Fe B alloy were taken as the research objects,and neutron irradiation experiment and high temperature experiment were carried out.X-ray,magnetic force microscope,M?ssbauer spectrometer and magnetic properties testing system were used to systematically characterize the structure and properties of the alloy,and the changes of the structure and properties of the permanent magnetic materials under irradiation and high temperature were obtained.Simultaneously,LAMMPS software was used to simulate the defect evolution process of pure Fe and Fe Ni alloys in the initial stage of irradiation.The results of neutron irradiation experiments show that the magnetic properties of Sm Co and Nd Fe B permanent magnet alloys undergoing 5×1014 n/cm2 neutron irradiation change about 1%,and their phase structures have not changed significantly.The electronic structure and magnetic domain structure of Sm Co hardly change before and after irradiation.The magnetic property test results show that the neutron radiation resistance of Sm Co alloy is better than that of Nd Fe B alloy.The magnetic properties of Sm Co alloy from room temperature to 550 oC and the magnetic properties of Nd Fe B alloy from room temperature to 300 oC were obtained through a high-temperature online demagnetization system.The magnetic properties of Sm Co and Nd Fe B permanent magnet alloys show a decreasing trend with increasing temperature,and the decreasing trend is different in different temperature intervals.At 550 oC,Br of the Sm Co alloy decayed to 78.2% at room temperature,and Hci decayed to 11.2% at room temperature.At 300 oC,Br of the high-coercive Nd Fe B alloy(N28EHC)decayed to 49.8% of room temperature,Hci to 1.5% of room temperature;Br of the high magnetic energy product Nd Fe B alloy(N52)to 23.4% of room temperature,Hci Decay to 0.1% of normal temperature.In the process of temperature increase,the degree of attenuation of remanence is smaller than that of coercive force.The magnetic domain morphology of Sm Co alloy after treatment at room temperature and 500 oC was observed by magnetic force microscope.At room temperature,in the direction perpendicular to the easy magnetization axis,the magnetic domain structure of the residual magnetic state Sm Co is a labyrinth domain.After 500 oC heat treatment,the magnetic domain arrangement becomes chaotic and no longer exhibits the characteristics of a labyrinth domain.Molecular dynamics was used to simulate the defect evolution process of pure Fe and Fe Ni alloys in the early stage of neutron irradiation.The defect evolution process includes ballistic stage,recombination stage and stable stage.Irradiation induces vacancies and interstitial atoms,and interstitial atoms are distributed around the vacancies.In the stabilization stage,the number of defects is small and the distribution is scattered.Irradiation makes the local environment of some atoms in the material change,but it does not cause phase transformation and amorphization.The increase of irradiation dose rate makes the number of defects in pure Fe increase.The increase of the energy of the primary collision atom(PKA)leads to the increase of the defect evolution time and the number of defects.The incident direction and ambient temperature of PKA have little effect on the evolution of defects.