Study On Crystallization Of Nd-Fe-B Alloy And The Relationship Between Magnetization And Orientation Degree Of Hot-deformation Nd-Fe-B Magnets

In this paper, the effects of pre-annealing temperature on the (Nd,Pr)12.8Dy0.2Co4.0Fe77.4B5.6amorphous alloyand the relationship between the magnetization and the orientation degree of hot-deformation Nd14Fe80B6nano-crystalline magnets were researched.The experiment results show that: when the (Nd,Pr)12.8Dy0.2Co4.0Fe77.4B5.6melt-spun ribbons crystallized, therich-rare earth phase and2:14:1hard phase are co-existed. The onset crystallization temperatures andcrystallization peak of (Nd,Pr)12.8Dy0.2Co4.0Fe77.4B5.6pre-annealed at803.0K for10min, measured by DSC atdifferent heating rates, are decreased compared with those of the original melt-spun ribbon. The crystallizationactivation energies at the onset crystallization temperatures, the peak one and the average crystallization index of(Nd,Pr)12.8Dy0.2Co4.0Fe77.4B5.6alloy pre-annealed at803K for10min is398.60KJ/mol,280.06KJ/mol, and2.45respectively. While that of the original melt-spun ribbon is398.54KJ/mol,342.75KJ/mol, and2.93respectively.The frequency factor at the onset crystallization temperatures, the peak one of (Nd,Pr)12.8Dy0.2Co4.0Fe77.4B5.6alloypre-annealed at803K for10min is5.27×1024min-1,7.98×1016min-1respectively. And that of the originalmelt-spun ribbon is2.22×1024min-1,4.30×1020min-1, respectively. But the crystallization rate constant at the onsetcrystallization temperature before and after pre-annealing of the (Nd,Pr)12.8Dy0.2Co4.0Fe77.4B5.6ribbon is almostthe same at the same heating rate. But the crystallization rate constant at crystallization peak temperature is greatlydecreased after pre-annealing. The maximum crystallization rate of (Nd,Pr)12.8Dy0.2Co4.0Fe77.4B5.6alloypre-annealed at803.0K for10min is significantly decreased compared with that of the original melt-spun ribbonat the same heating rate. It is concluded that the atomic activity at the peak temperature is significantly reduced, sois the growth rate, and the process of crystallization is restrained after pre-annealing at803K for10min, comparedwith those of the original melt-spun ribbon.As the deformation temperature from1113K to1163K, the orientation degree of Nd14Fe80B6hot-deformednano-crystalline magnets is firstly increased and then decreased. The orientation degree has been introduced to theformula of the saturation magnetization. And the relationship between the magnetization and the orientationdegree of the magnets has been established when applied magnetic field respectively at2T,5T. The relationshipcan be described as following function:M S2(1) M ST010.351080.1862224respectively. It is observed that the coarse grain belts anddisorientation areas exist in the magnets. If they are eliminated, the orientation degree and the magnetic propertieswill be improved.