Microstructures And Magnetic Properties Of Nd₂Fe₁₄B/Fe₃B Nanocomposite Materials

In this work,the effects of quenching wheel speed and crystallization annealing process on the microstructure and magnetic properties of Nd₉Fe₇0Ti₃C₁Nb₃B₁₄ nanocomposite permanent alloys have been investigated.By using X-ray diffraction?XRD?,differential scanning calorimeter?DSC?,Physical Property Measurement System?PPMS?and J ADE,MAUD anylysis software.The main research results are as follows:A series of Nd₉Fe₇0Ti₃C₁Nb₃B₁₄ melt-spun ribbons were prepared by rapid quenching at different wheel speeds(Vs= 10,15,20,25,30 m·s^-1).The results show that there exists a critical quenching wheel speed Vc,which is between 15 m·s^-1 and 20 m·s^-1.And when their Vs is below the Vc,the ribbons?named low quenching speed ribbons?consist of amorphous phase and a little amount of Nd₂Fe₁₄B,Fe₃B and ?-Fe phases,but when their Vs is above it,the ribbons?named high quenching speed ribbons?do complete amorphous one.Its thermal stability is enhanced with increasing the Vs.The effect of quenching speed on the crystallization phase transition have be studied.The crystallization phase transition of low and high quenching speed ribbons could be deduced respectively as follows: AP?amorphous?+Nd₂Fe₁₄B+Fe₃B+ ?-Fe ?Nd₂Fe₁₄B+Fe₃B+?-Fe+Nd₃Fe₂₀B₂?Nd₂Fe₁₄B+Fe₃B+ ?-Fe;and AP?amorphous?? AP?+ Nd₃Fe₂₀B₂ ? Fe3B+Nd₃Fe₂₀B₂? Nd₂Fe₁₄B+Fe₃B+ ?-Fe.The effect of annealing temperature on the magnetic properties of Nd₉Fe₇₀Ti₃Nb₃B₁₄ melt-spun samples have been investigated.Research shows that: with the increase of annealing temperature,the magnetic properties of melt-spun samples becomes bigger first then gets smaller.Each of melt-spun sample has a optimum annealing temperature.The optimum annealing temperature?1060 K?about the high quenching speed melt-spun samples higher than 1010 K about the low quenching speed melt-spun samples.After the optimal annealing,the grain size of the low quenching speed melt-spun samples finer than the high quenching speed melt-spun samples.The optimum coercivity and energy product of the former are 28.41% and 20.12% higher than that of the latter respectively,although their remanence values are very close.The effect of annealing time on the magnetic properties of Nd₉Fe₇₀Ti₃Nb₃B₁₄ melt-spun samples have been investigated.Research has shown that low quenching speed melt-spun samples and high quenching speed melt-spun samples which after annealing phase composition are Nd₂Fe₁₄B,Fe₃B and?-Fe phases.As the extension of annealing time,the content of Nd₂Fe₁₄B phase of melt-spun samples increased,the content of?-Fe phase of melt-spun sampl-es decreased,the grain size gets larger and the magnetic properties of melt-spun samples becomes bigger first then gets smaller.After the optimal annealing,the optimum coercivity and energy product of the low quenching speed melt-spun samples are 48.06%and 34.49% higher than that of the high quenching speed melt-spun samples respectively,although their remanence values are same.