Research On Hydrogenation-Disproportionati On Mechanism And Microstructure Study Of Nd₁₄Fe_66.9B₇Co₁₁Zr_0.1Ga_1.0 At Room Temperture

This paper based on mechanical milling–HDDR processing, a new technique proposed by our group, to obtain high magnetic properties through addition of Co,Zr and Ga. Hydrogenation-disproportionation of Nd-Fe-B-Ga-Co-Zr alloy by mechanical milling in hydrogen and disproportion knetics were investigated systematically. Desorption-recombination at selected temperature in vacuum and magnetic properties were investigated simplely.Microstructure changes of annealing Nd₁₄Fe_66.9B₇Co₁₁Zr_0.1Ga_1.0 alloy were characterized by SEM and EDS analysis. The results showed thatα-Fe in as-cast were eliminated. Microstructural changes of annealing Nd₁₄Fe_66.9B₇Co₁₁Zr_0.1Ga_1.0 alloy during mechanical milling in hydrogen were characterized by XRD and TEM analysis. The results showed that Nd₁₄Fe_66.9B₇Co₁₁Zr_0.1Ga_1.0 alloy can be disproportionate into Nd2H5,Fe(Co)B andα-Fe(Co) after 20 hours, and the size of the annealing disproportionated phases is about 8 nm after full disproportionation. Disproportionated phases and relative content were characterized by M?ssbauer during different milling time. The results showed that Nd2H5 is about 2.6%, Fe(Co)B is about 16.5% andα-Fe(Co) is about 80.9%. The morphology of the powders millied in hydrogen was characterized by SEM. It was found that the particle size of the NdFeBCoZrGa alloy powders decreased obviously during milling in hydrogen and the size of particle after full disproportionated is about 600nm.Disproportionation kinetics equation was founded. That rotate velocity of milling and ball to powder ratio influence on capability of disproportionation kinetics were studied systematically. The results showed the higher of intensity milling the faster of disproportionation velocity, and full disproportionation required less time. At the same rotate velocity of milling, large ball to powder ratio milling required less time to accomplish full disproportionation; at the same ball to powder ratio, high rotate velocity of milling required less time to accomplish full disproportionation.With the help of XRD, the desorption-recombination behaviour of annealing disproportionated NdFeBCoZrGa alloy powders was investigated simply. The results showed that nanocrystalline magnetic material with average grain size of about 23nm was obtained by desorption-recombination processing at 760℃for 30 min. The result showed that B_r=0.74T and _iH_c=624.5KA/m and (BH)_m=125KJ/m³.