Effect Of Adding Rare Earth Ho Alloy To Grain Boundary On Microstructure And Properties Of NdFeB Regenerated Magnet

NdFeB permanent magnet is widely used in information technology,medical equipment and daily electrical appliances due to its unconventional magnetic properties;and with the expansion of science and technology,the requirement for NdFeB magnets keeps on increasing.However,NdFeB magnets in the production and machining will manufacture a great deal of waste magnets.At the same time,the anterior NdFeB permanent magnet products are gradually invalidated and scrapped.These are the primary origin of waste magnets.Because the rare earth content in the waste NdFeB magnets is greater than that in the original ore,so it has important economic value to recycle and reuse them through technology.Therefore,this paper improves the performance of the regenerated magnet by adding rare earth Ho alloy to the grain boundary,and explores the technology of recycling the block waste.Finally,the main conclusions are as follows:（1）The effect of low melting point Ho_63.3Fe_36.7alloy at grain boundary on the structure and properties of NdFeB regenerated magnet was studied.The results show that the optimal distribution of grain boundary phases is obtained at the addition amount of 2 wt%in Ho_63.3Fe_36.7alloy,which weakens the exchange coupling effect between the main phases.Meanwhile,the shell structure of（Pr,Nd,Ho）₂Fe₁₄B at the boundary of the Nd₂Fe₁₄B phase is formed by diffusion of Ho in the grain boundary phase,which increases the H_Aof the main phase,and the coercivity of the NdFeB magnet is increased by 1.55 KOe（about 9.1%）,and the remanence is decreased by 0.18 kGS（1.4%）.In addition,the addition of Ho_63.3Fe_36.7 alloy can improve the wave absorption performance of NdFeB regenerated magnet,realizing the goal of turning waste magnets into treasures.（2）The effect of adding low melting point Ho_69.3Ni_30.7 alloy at grain boundary on the structure and properties of regenerated magnets was studied by changing the aging process.It is found that the addition of Ho_69.3Ni_30.7alloy meliorates the layout and shape of grain boundary phase,and the rare earth Ho in the alloy is enriched in the boundary layer of the 2:14:1 main phase grain,thus forming a rich shell with high H_A.When 2 wt%Ho_69.3Ni_30.7is added,the coercivity of the magnet increases from 15.11 kOe to 16.35 kOe（increases by 8.2%）,and the remanence decreases from 12.38 kGS to 11.98 kGS（decreases by 3.2%）.Moreover,with the addition of Ho_69.3Ni_30.7,the Curie temperature and reflection loss of the regenerated magnet are also increased.The research provides a reference for improving the coercivity,Curie temperature and absorbing performance of waste NdFeB magnets.（3）The effect of aging temperature on regenerated NdFeB magnet with 2 wt%Ho_63.3Fe_36.7was studied.The two-stage aging temperature of the regenerated magnet was selected in the range of 860℃～960℃and 450℃～540℃.It was found that the aging temperature could turn the microstructure and structure of the magnet to affect the coercivity of the regenerated magnet.And the optimal aging process is 900℃×2h+460℃×1.5h.In addition,aging temperature can also affect the absorption performance of NdFeB regenerated magnet.