Preparation,Microstructure And Magnetic Properties Of ThMn₁₂-type Rare Earth Permanent Magnet

ThMn12-type permanent magnet materials attracts extensive attention due to excellent intrinsic properties,low rare earth content and low cost.However,how to convert its intrinsic properties to external properties is the critical problem facing the research of ThMn12-type permanent magnet.In this work,the amorphous-nanocrystalline Sm Fe12-based alloys were prepared by arc-melting,meltspunning,hot pressing and deformation technology.The relation between the composition,preparation process,microstructure and magnetic properties of the alloys were studied.The effects of Sm content and Nb,Ti,V substitution on the phase structure,microstructure and magnetic properties of Smx Zr0.2(Fe0.8Co0.2)11.5-y Ti0.5My(x=0.8-1.2,M=Nb,Ti,V,y=0-0.4)alloys were analyzed.The conclusions are as follows:Firstly,Smx Zr0.2(Fe0.8Co0.2)11.5Ti0.5(x=0.8-1.4)alloy ingots were prepared by arc-melting.It was found that the content of hard magnetic 1:12 phase and soft magnetic ?-(Fe,Co)phase decreased with the increasing Sm content,and a large amount of 1:10 phase appeared.The effects of Sm content and heat treatment on the phase structure and coercivity were studied.The coercivity of the ribbons after heat treatment increased with the increasing Sm content.For x=1.2,the largest coercivity of 3.0 k Oe was obtained in x=1.2 alloys.It is proved that the increasing of Sm content might introduce the nonmagnetic intergranular phase.Secondly,the substitution of Nb,Ti and V elements significantly improved the stability of 1:12 phase.For Sm1.2Zr0.2(Fe0.8Co0.2)11.1Ti0.9 alloy,the content of 1:12 phase reached 91 %.In addition,Nb,Ti and V elements significantly increased the coercivity of the alloy ribbons after heat treatment,the largest value of 5.0 k Oe was obtained in Sm1.2Zr0.2(Fe0.8Co0.2)11.1Ti0.5Nb0.4 alloy.Thirdly,bulk magnets were prepared by hot-pressing and deformation process.The magnets were made by hot pressing process could effectively suppress the precipitation of soft magnetic ?-(Fe,Co)phase,the collapse shoulder of demagnetization curve disappeared.For Sm1.2Zr0.2(Fe0.8Co0.2)11.3Ti0.5Nb0.2,the coercivity,remanence and maximum magnetic energy product are 3.4 k Oe,0.79 T and 58.1 k J/m3 respectively.In addition,the addition of low melting point alloys Cu-Ga and Cu-Ga-Ti as grain boundary diffusion results in the destruction of the structure of the ThMn12 1:12 phase,which cannot improve the magnetic performance of the magnets.Finally,the anisotropy of the magnets were successfully induced by the process of the hot deformation.