Microstructure And Magnetic Properties Of SmCo₅ Based Multi-phase Ribbon Magnets

SmCo₅ magnet has been received widely attention due to its high magnetocrystalline anisotropy,high Curie temperature and excellent thermal stability.In this paper,it is proposed to optimize the alloy composition by introducing decomposition-type alloys into the SmCo₅ matrix with high anistropic field.We utilize the phase transitions of alloys and their interactions with the SmCo₅ phase to establish a novel SmCo₅-based multi-phase microstructure,and hope to develop a new permanent magnet.The SmCo₅+x wt%Al-Cu-Fe?x=0,3,5,7?and SmCo_5-yCu_y?y=0,0.1,0.3,0.5?+5 wt%Alnico5 multi-phase composite ribbons are prepared by arc-melting,melt-spinning and annealing method.The influence of melt-spinning speeds,alloy composition and annealing process on the microstructure and magnetic properties of ribbons are studied by means of X-ray diffractometer,scanning electron microscopy,transmission electron microscopy,vibrating sample magnetometer and physical property measurement system etc.The experimental results show that in the composite ribbons melt-spun at a speed of40 m/s,the intrinsic coercivity increases first and then decreases,and the magnetization gradually increases with increasing the content of Al-Cu-Fe alloy,finally the magnetic properties reach the optimal values when x increases to 3,i.e.,H_c=17.6 kOe,M_r=39.1emu/g,M_2T=45.2 emu/g.The microstructure and magnetic properties of SmCo₅+3 wt%Al-Cu-Fe ribbons melt-spun at 10 m/s,25 m/s and 40 m/s are studied.The grain size gradually decreases,the coercivity and the magnetization gradually increase with an increase in melt-spinning speeds,and the ribbons melt-spun at 40 m/s have the best magnetic properties.The SmCo₅+3 wt%Al-Cu-Fe ribbons melt-spun at 40 m/s and followed by annealing at 600°C for 30 min obtain the outstanding magnetic properties,i.e.,H_c=29.7 kOe,M_r=37.1 emu/g,M_9T=46.7 emu/g.Meanwhile,the precipitations of Sm₂Co₁₇,Al₉Co₂,Al₁₃Co₄ and Sm₂Co₇ phases at the grain boundaries enhance the coercivity by pinning the domain walls of Sm?Co,M?₇ matrix.The effect of Cu content on the microstructure and magnetic properties of SmCo_5-yCu_y?y=0,0.1,0.3,0.5?+5 wt%Alnico5 composite ribbons melt-spun at a speed of 40 m/s are investigated.Their coercivity and the magnetization increase first then decrease with the increase of Cu content.The ribbons obtain the excellent magnetic properties when y=0.3,namely H_c=24.6 kOe,M_r=55.9 emu/g,M_9T=69.1 emu/g.The SmCo_4.7Cu_0.3+3 wt%Alnico5ribbons annealed at 600°C for 30 min obtain the better hard magnetic properties,namely H_c=30.1 kOe,M_r=41.6 emu/g,M_9T=54.2 emu/g.