Preparation And Magnetic Properties Of （Sm,R）（Fe,M）₁₂ Alloys

ThMn12-type rare earth magnetic alloys has lower rare-earth content,higher Curie temperature and higher magnetic energy product than Nd2Fe14B,and has become the research focus of the latest generation of permanent magnet materials.However,ThMn12-type rare earth magnetic alloys generally have low coercivity and cannot meet the service requirements of actual permanent magnet materials,which is the main bottleneck restricting their development.In this paper,(Sm,R)(Fe,M)12 is used as the research object and the effects of the substitution of stabilizing elements M=Ti/Si,rare earth elements R=Y/Ce and the preparation process on the microstructure and intrinsic magnetic properties of(Sm,R)(Fe,M)12 magnetic alloys were studied systematically.The preparation of SmFe11Ti bulk magnetic material by SPS method was initially tried,which provides a reference for the research and development of high Hc of ThMn12-type rare earth magnetic materials.The specific research contents are as follows:(1)SmxY1-xFe10Si2(x=0.1～0.5)alloys were prepared by the method of arc melting.The coercivity is found to increase with the increment of Sm content,and the more α-Fe soft magnetic phase emerges.The α-Fe phase mainly existed as the precipitates within the grains and possesses a good lattice match with the main phase of SmxY1-xFe10Si2.The large amount of precipitation of α-Fe phase has an adverse effect on the coercivity of the material.The formation of α-Fe soft magnetic phase could be effectively suppressed by controlling the quenching rate by strip casting.The highest coercivity of Hc=2.13 kOe was obtained for Sm0.5Y0.5Fe10Si2 sample at an optimum wheel speed of 35 m/s.(2)The homogenization heat treatment can promote the sufficient crystallization of Sm0.4Y0.6Fe10Si2 hard magnetic phase,and it is found that α-Fe soft magnetic phase will continue to precipitate from the alloy during the heat treatment,resulting in the increase of the proportion of soft magnetic phase and the deterioration of hard magnetic properties.Therefore,it is very important to balance the crystallization of the Sm0.4Y0.6Fe10Si2 phase and the precipitation of the α-Fe soft magnetic phase to the positive and negative contributions to the coercivity.the optimum coercivity of Hc=2.70 kOe was obtained for the Sm0.4Y0.6Fe10Si2 sample at a heat treatment condition of 900℃ for 30 min.(3)The relationship between the magnetic properties and microstructure of(Sm1xCex)Fe11Ti(x=0～0.2)samples were investigated.It is found that the introduction of highabundance rare earth Ce maintains the stability of the ThMn12 phase structure,but the magnetic properties of the samples deteriorated severely,and its highest coercivity is only Hc=0.28 kOe.The surface of the SmFe11Ti alloy magnetic powder is plated with Cu and sintered into a dense bulk magnet by SPS.The Cu-rich grain boundary phase of the sintered magnet is constructed by the Cu coated on the surface of the magnetic powder.Finally,the coercivity of bulk magnets was effectively increased to Hc=2.90 kOe.