Study On Microstructures And Performance Optimization Of (Sm_1-xRe_x)Co₅ Permanent Magnets

SmCo₅permanent magnet,limited by cobalt as a strategic metal,has small output and high production cost.However,SmCo₅permanent magnet has excellent performance and chemical stability in high temperature and harsh service environment,which makes it widely used in aerospace,military and other high-tech fields.How to optimize the performance and cost of SmCo₅permanent magnet has become a hot research topic.It is found that Pr Co₅and YCo₅permanent magnets have excellent magnetic properties in Re Co₅based permanent magnet materials.It's a good choice to replace some Sm elements in SmCo₅with Pr and Y elements to prepare high-performance(Sm_1-xRe_x)Co₅permanent magnet.In this paper,Sm_1-xY_xCo₅and Sm_0.6Pr_0.4Co₅sintered magnets were prepared by traditional powder metallurgy liquid phase sintering method through adjusting composition and optimizing process.The relationship between microstructure and magnetic properties of the magnets was studied.Firstly,Sm_0.7Y_0.3Co_zand Sm_0.5Y_0.5Co₅sintered magnets with SmCo_1.7liquid phase added into the main phase of Sm_1-xY_xCo₅were prepared.The effects of z value,content of liquid phase alloy and sintering process on the magnetic properties and microstructure were investigated.The magnetic properties results of Sm_0.7Y_0.3Co_zand Sm_0.5Y_0.5Co₅sintered magnets show that the more Y content in the magnets,the lower the magnetic properties.Sm_0.7Y_0.3Co_zand Sm_0.5Y_0.5Co₅magnet.The H_Aof Sm_0.7Y_0.3Co_zingot and Sm_0.5Y_0.5Co₅ingot is 286.4 k Oe and 210.4 k Oe respectively.When the value z is 4.76,the liquid phase addition is 6 wt%and the sintering temperature is 1150?,the magnetic properties of Sm_0.7Y_0.3Co_zare the best:B_r=9.4k G,H_cj=18.3 k Oe,(BH)_max=22.0 MGOe,and the density is 8.13 g/cm³.When the sintering temperature is 1160?,the magnetic properties of Sm_0.5Y_0.5Co₅are the best:B_r=8.8 k G,H_cj=13.7 k Oe,(BH)_max=20.2 MGOe,and the density is 7.76 g/cm³.The results of XRD calculation and EBSD crystal orientation show that Sm_0.7Y_0.3Co_zand Sm_0.5Y_0.5Co₅has a good(00l)crystallographic orientation.Secondly,Sm_0.6Y_0.4Co₅permanent magnet was prepared,and the effect of liquid phase on the properties and microstructure of sintered magnet was investigated.The properties of magnets with different heat treatment processes were studied under the condition of same composition.The magnets with excellent properties were prepared and the differences of microstructure were analyzed.When the liquid phase addition is 6 wt%and the sintering temperature is 1150?,the magnetic properties of Sm_0.6Y_0.4Co₅are the best:B_r=10.5 k G,H_cj=20.6 k Oe,(BH)_max=22.2 MGOe,and the density is 8.27 g/cm³.The squareness of demagnetization curve of magnet needs to be improved.At 25-200?,the remanence temperature coefficient?is-0.06%/?,and the coercive force temperature coefficient?is-0.37%/?.The magnet mainly consists of 1:5 main phase and a small amount of R-rich phase.The XRD results show that the orientation peak becomes stronger and the degree of orientation is I₍₀₀₂₎/I₍₁₁₁₎=51.40,indicating that the orientation of the magnet is better.EBSD results also show that the orientation of the grains is close to(00l)orientation.