| Sm2Co17 permanent magnet alloy provides magnetic field in precision instrument,such as gyro,accelerometer,etc.The stability of its magnetic property is directly related to the accuracy of the instrument.In this paper,the magnetic stability of Sm2Co17 alloy was studied.During natural storage and use,the domain evolution and its correlation with the magnetic stability were studied.The magnetic degradation behavior of Sm2Co17 alloy was tested by nondestructive testing equipment of hard magnetic materials.The evolution of magnetic domain was studied by magneto-optic Kerr electron microscope and lorentz electron microscope.Since temperature is one of the main reasons for the degradation of magnetic properties,this paper analyzes the morphology and evolution of magnetic properties in the magnetic domain by temperature field.The analysis and test results of Sm2Co17 alloy samples with natural storage life of 3 years,7 years,9 years,13 years and 16 years showed that the grain size and phase composition of the alloy did not change with the change of storage time,and the magnetic properties of samples in each year were tested for 306 days,and the magnetic properties fluctuated within the error range,and no obvious degradation was observed.The results of lorentz transmission electron microscope show that domain walls can be found in samples with storage time of 16 years,which proves that domain inversion occurs.The results of accelerated aging with constant temperature field at70?,90?,120?,180?,240?and300?show that no reverse magnetic domain can be produced when the ambient temperature of the sample is at or below 180?.Under the action of temperature field,domain inversion has time effect.Insulation at240?and 300?can produce irreversible domain inversion,which is related to the duration of temperature action.The effect of temperature field cannot be accumulated,and the longer the temperature field lasts,the more obvious the nucleation growth of the reverse magnetic domain is.The magnetic properties of SmCo alloy will decline rapidly in a short time at the beginning of accelerated aging.After 24h,the magnetic properties of SmCo alloy are basically in a stable state at all temperatures,and the decay rate is very slow.Within the temperature range of 70?300?,the magnetic loss rate is 2.48×10-2%/h-14.84×10-2%/h in the first 24h,and 0.92×10-4%/h-10.32×10-4%/h after 24h,a difference of two orders of magnitude.The evolution of magnetic domain under thermal activation was observed by using lorentz transmission electron microscope heated to 500?.The movement behavior of the wall of the magnetic domain is a jump directly between the cell walls,rather than a continuous movement,which proves that the SmCo5 phase is the pinning point,and the cell wall can only jump between the SmCo5 phase.The reverse domain nucleation caused by temperature field is based on crystal cell,which has two processes of nucleation and growth.Only when a certain temperature continues to act for a certain period of time can the magnetic moment reverse be caused.The reverse domain diffuses with crystal cell as the unit,and the domain wall moves with SmCo5phase as the pinning point.The non-destructive testing equipment of hard magnetic materials was used to test the results.It was found that when the aging temperature increased,the magnetic properties decreased.When the aging temperature was lower than 120?,the magnetic properties changed reversibly,and the magnetic properties recovered when the temperature returned to room temperature.In the range of 120?-180?,the magnetic properties will have irreversible degradation,but the reverse domain cannot be observed.The magnetic properties change irreversibly in the insulation process of240?and 300?,and the above reasons may be related to whether the magnetic moment deflection can cross the energy barrier. |
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