| Along with the computer, transportation, communication, aerospace and other modern technology to the rapid development of magnetic performance demand is higher and higher, the demand is growing too. The anisotropic NdFeB magnetic powder is more idea material on production application. HDDR(hydrogenation-disproportionation-desorption-recombination) process is an effective means by which the high performance and anisotropy Nd2Fe14B-base magnetic powder can be made, That important technological process is attentioned by the domestic and foreign research scholar. In this text, the reseach focus on component change after HDDR, the influence rules of HDDR process and the additive element on the magnetic performance are studied.In this paper, we using the mid-frequency induction furnace in the vacuum, Nd12.5Fe79.9-xCoxB6.5Zr0.1Dy1.0(x=14、15、16、17),Nd13Fe63.9-xCo16B6.5Zr0.1Ga0.5Tix(x=0、0.5、1、1.5) and Nd13-xFe63.9Co16B6.5Zr0.1Ga0.5Dyx(x=0、0.5、1.5) alloy are smelted. These alloys across different HDDR process, using X-ray diffraction and high field pulse magnetic field meter test enginery to find influence rule after the additive element Co, Ti and Dy changed. Under different conditions HDDR processing, researching the influence between various magnetic properties and component change.In this thesis, The additional element Co is helpful for the whole properties and anisotropy’s improvement, and when content of Co reaches16percentages, the properties are best. When the next process is taken:25℃×0.1MPa×60min'480℃×0.06MPa×20min'810℃×0.03MPa×120min'830℃×high vacuum×30min'quenching, the magnetic properties of Nd12.5Fe79.9-xCoxB6.5Zr0.1Dy1.0(x=14、15、16、17) alloy can reach:(BH)m=184.51kJ/m3, Br=1.393T,jHc=345.5kA/m, DOA=0.729.The additional element Ti is helpful for the improvement of (BH)m, Br, jHc and anisotropy, and when the content reached0.5percentages the properties are best. Fe is partly replaced with Ti can improve fine grains and the organizational structure of riching Nd phase. When the following process is taken:25℃×0.1MPa×60min'820℃×0.03MPa×150min'830℃×high vacuum×30min'quenching, the magnetic properties of Nd12.5Fe79.9-xCoxB6.5Zr0.1Dy1.0alloy can reach:(BH)m=183.40kJ/m3, Br=1.133T, jHc=933.7kA/m, DOA=0.334The additional element Dy can abvious advance the alloy’s whole properties and anisotropy, but (BH)m and Br are significantly first increase then reduce in trend, and when content of Dy reaches0.5percentages, the properties are best. When the following HDDR technique is taken:25℃×0.1MPa×60min'800℃×0.03MPa×140min'820℃×high vacuum X30min'quenching, the magnetic properties of Nd13-xFe63.9Co16B6.5Zr0.1Ga0.5Dyx (x=0,0.5,1.5) alloy can reach maximum magnetic properties.In this experiment we did the research on the influence of different stages of HDDR technique on the properties of the Nd12.5Fe63.9Co16B6.5Zr0.1Dy1.0alloy composition. HDDR technique is divided into two parts:HD and DR. The phase changes of NdFeB alloy through HDDR technique are shown below:in original casting ingot there is big NdFeB phase, after HD process the NdFeB phase disproportionationed into the next three phase:NdH2、α-(Fe,Co) and (Fe,Co)2B, and after HDDR technique, the three disproportionation produts are recombined into fine NdFeB phase, the phase reaction as follows:2NdH2+12a-(Fe,Co)+(Fe,Co)2B'Nd2(Fe,Co),4B+2H2.Through the research on HD and DR part, we find there are little influence on the magnetic properties by changing temperature of HD’s high temperature stage; warming way has more influence and dehydrogenation time. Heating rate is helpful for the whole properties and anisotropy’s improvement, and when there is appropriate heating rate can reache the best properties. The temperature of HD’s high temperature can obviously advace the alloy’s magnetic properties, the best temperature of HD’s high temperature is800-830℃. The results indicate that:in the HDDR process, disproportionation time is the key to cause materials to produce anisotropy, and when the disproportionation time reaches30min, the properties are best. |
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