Add Element Of Ga On The Influence Of The Microstructure And Magnetic Properties Of Sintered Nd-fe-b Permanent Magnet

Sintered Nd-Fe-B-type permanent magnets are the most powerful in magnetic performance up to now. In laboratory and industry, the maxium (BH)max have reached 444kJ/m3 and 398kJ/m3 (theoretical maxium (BH)max =525.4kJ/m3)respectively at the present. But the capability of resisting demagnetization is poor, Its intrinsic coercivity is about one third of theoretical coercivity (theoretical coercivity =5572kA/m),so improving coercivity of sintered Nd-Fe-B-type permanent magnets is one of the most important technique in improving its magnetic performance and expanding its applicability.In the thesis, By using x-ray diffraction, energy spectrum analysis, metallographical analysis and scanning electron microscopy and opitimzing technology, the effects of the element Ga was researched and discussed in the magnetic performance and microstructure of Sintered Nd15Fe78B7+Ga permanent magnets made by powder metallurgy.The feasible technology and its processing parameter of Nd15Fe78B7+Gawere determined by experiments. The result were followed: technological process adopted traditional powder metallurgy sintered technology and two-stage tempering technology; cooling was furnace cooling between sintered and the first stage tempering; cooling was wind cooling between the first stage tempering and the second stage tempering and after the second stage tempering; sintering temperature was 1110℃,sintering time was 60 min; the first stage tempering temperature and tempering time were 900℃ and 60min respectively; the second stage tempering temperature and tempering time were 600℃ and 120min respectively.By analysing magnetic performance and microstructure of sample in experiment, two conclusions were obtained. For Nd15Fe78B7+Ga permanent magnets, one was that intrinsic coercivity Hci was not only increased greatly, but also remnant magnetism Br and maxium (BH)max were not deceased when the amount of doped-Ga was not greater than 1.0wt%. when the amount of doped-Ga was 0.25wt%, Br get to maxium1.120T; when the amount of doped-Ga was 1.0wt%, Hci reached maxium 523kA/m; when the amount of doped-Ga was 0.5wt%, (BH)max arrive to maxium 230kJ/m3.Considerating over-all performance of mag nets, it was concluded that the optimal amount of doped-Ga was 0.5wt%. The other was that the grains size distribution of grains was narrow and grain distributed homogeneously as to microstructure of magnets when the amount of doped-Ga was 1 .Owt% ; (3 ) In the magnets, there existed not only Nd2Fei4-xGaxB, but also GaNd concerning the Ga-elment form. The GaNd increased the amount of liquid and had favorable function during sintering, so it made for the increase of magnet's density and the form of the second phase is good for improving coercivity.By doped-Ga,the coercivity and the courier temperature of sintered Nd-Fe-B-type permanent magnets were increased without losing (BH)max. it made the temperature property improve of sintered Nd-Fe-B-type permanent magnets and it had important significance to promote improvement of over-all performance of sintered Nd-Fe-B-type permanent magnets.