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Basic composition and microstructure of sintered ndfeb magnet

by:Newland     2020-04-15
Sintered ndfeb ( 钕铁硼) Or neodymium magnets ( Nd) Magnet, as the name suggests, contains the necessary rare earth neodymium. Neodymium iron atoms and ferromagnetic elements ( Iron) The coupling of the atom, helps to obtain high remanence (magnets BR) And the maximum energy product ( BH) Max, which make it compared with other permanent magnet is unusual. In business of sintered NdFeB magnet, neodymium usually be replaced by other rare earth elements in part, including praseodymium ( Praseodymium) , dysprosium ( Dysprosium) And terbium ( Terbium) Wait, because praseodymium and neodymium element often coexist in the ore, the two elements with similar physical and chemical properties, therefore, instead of pure metal neodymium rare earth permanent magnet alloy production of rare earth permanent magnet alloy is more economic. Due to the ratio of the Nd/Pr is about 4:1 in the ore, so in most commercial magnets Nd/Pr ratio is about 4:1. With Dy and ( Or) Tb elements instead of Nd elements can significantly improve the coercive force of the material ( Hcj or Hci) 。 Due to high costs and great loss of Br, Dy, Tb elements of total content in the magnet is usually less than 10 wt %. Generally speaking, the total content of rare earth elements in magnet about 30 wt %, the material cost accounts for about 70% of the magnet, is even higher, depending on the specific content of rare earth elements and their. Besides and neodymium iron boron element of sintered ndfeb magnet is also essential. Although B element content of a magnet is only about 1 wt %, but for its magnetic can remain stable, we must ensure the stability of the intermetallic phase. In addition, in order to improve the thermal stability and corrosion resistance of alloy, with a small amount of cobalt ( Co) Elements instead of iron, and add a small amount of aluminum ( Al) And copper ( Cu) Elements to improve the uniformity of the organization of alloy, thus improve the alloy Hcj and ( BH) 上限。 From X-ray diffraction of sintered ndfeb magnet ( XRD) Spectra can be seen that Nd2Fe14B sifang facies is the main phase of magnets. Scanning electron microscopy ( SEM) Image display, dark grey area for Nd2Fe14B grain, and the average grain size of about 6 - Light grey zone around 8 microns, grain for a nickel, grain boundary between adjacent grain average thickness of the grain boundary is about 10 nm, such as transmission electron microscopy ( TEM) As shown in the image. Sintering process of sintered ndfeb magnet is, in fact, the liquid phase sintering process. Grain boundary phase melting point is lower than the grain boundary phase, in the process of sintering and subsequent annealing will melt as liquid phase, so the magnet densification and improve the organization to improve its magnetic uniformity is important. Relevant magnet product column recommended; Ndfeb regular shape magnet guess you might also interested in the following articles; The composition of the magnet element ( Components) And its characteristics have? Magnet primary ( Ndfeb and ferrite)
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