Optimization Of Microstructure And Magnetic Properties By Co Ga Dopant Nanocomposite Pr₂Fel₄B/α-Fe Alloy

Nanocomposite permanent magnet is a kind of new permanent materials that is formed by exchange couple interaction of adjacent atoms’magnetic moment, composition between soft magnetic phase of high saturation magnetization and hard magnetic phase of high anisotropy in nanoscale. Compare with traditional permanent magnet, nanocomposite permanent magnets have the advantages of low rare earth concentration, low cost, hard magnetic phase’s high coercivity and soft magnetic phase’s high saturation magnetization. It both has improvement between temperature stability and oxidation resistance. It could become a new generation of high property rare earth permanent magnet.This paper use processes that melt-spinning and crystallization heat treatment to prepare Pr-Fe-B/a-Fe nanocomposite permanent magnet and use methods that VSM、 XRD、AFM、SEM&EDS、TEM to study the magnetic property,phase composition and microstructure of alloy influenced by quenching speed, trace elements addition and annealing.First, phase composition and magnetic property of alloy is significantly influenced by quenching speed. Under optimal quenching speed, the hysteresis loops of alloy reveal typical single-phase characteristic. If the quenching speed is too low or high, the hysteresis loops of alloy reveal two-phase characteristic.1#alloy has the best magnetic property at34m/s, if the quenching speed is higher or lower than34m/s, it has certain bad influences for magnetic property of alloy. The best magnetic property of1#alloy is:Mr/Ms=0.749,(BH) max=56.56(kJ/m3), jHc=452(kA/m), Br=0.749(T).Secondly, the addition of CoGa in Pr-Fe-B alloys increase the remanence, intrinsic coercivity and maximum energy product. Compare with Pr-Fe-B alloys, the remanence, intrinsic coercivity and maximum energy product of Pr-Fe-Co-Ga-B alloys were increased by13.1%、12%and31.8%respectively.In the process of amorphous crystallization Pr-Fe-B/a-Fe alloys, it is significantly affected to materials’microstructure and magnetic properties that time and temperature of annealing. When the temperature is680℃and the time is8min, the addition of CoGa in Pr-Fe-B alloys has the best magnetic properties. Whatever the temperature is too low or high, the time is too long or short, it will damage the microstructure of alloys, decrease the magnetic property of alloys.Compare with magnetic properties of alloys with different composition, melt-spun with different wheel speeds and annealed at different temperature, the optimum magnetic properties of Pr-Fe-Co-Ga-B can obtained at22m/s,680℃and8min, The best magnetic property of10#alloy is:Br=0.836T(8260Gs), jHc=526.3kA/m(6600Oe),(BH) max=75.45kJ/m3(9.55MGOe).