共查询到18条相似文献,搜索用时 62 毫秒
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研究了NdFeB粉末中添加1wt%Dy2O3粉末对烧结NdFeB磁体微观结构的影响,研究发现,在烧结过程中,Dy2O3中的Dy与Nd2Fe14B中的Nd发生了置换反应,Dy进入Nd2Fe14B相,形成了(Nd,Dy)2Fe14B相,提高了磁体的矫顽力。 相似文献
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决定烧结NdFeB系永磁体矫顽力大小的因素 总被引:4,自引:0,他引:4
1前言提高烧结钕铁硼永磁体的磁性能,改善其使用性能,一直是磁性材料研究者和制造者追求的目标。关于高磁能积磁体的研究较多,也得到了某些应用,提高矫顽力方面的研究也不少,但研究进展缓慢。决定矫顽力大小的因素及其形成机理比较复杂,目前公认的说法有形核机理和钉扎机理,其中形核机理较好地解释了烧结NdFeB磁体。决定烧结NdFeB系永磁体矫顽力的因素有磁晶晶粒各向异性场、散磁场、边界显微结构、晶粒大小和晶粒错取向。提高矫顽力不仅可以提高其退磁能力,还可以提高其温度稳定性,降低磁通不可逆损失和矫顽力温度系数。2形核… 相似文献
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烧结NdFeB磁体的矫顽力 总被引:1,自引:4,他引:1
综述了近几年有关NdFeB磁体矫顽力形核机制与钉扎机制的主要观点和有关实验,重点介绍了矫顽力与晶界结构的关系和富Nd相对磁体碰硬化的重要作用。 相似文献
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烧结温度对电场烧结NdFeB合金显微结构的影响 总被引:1,自引:0,他引:1
对NdFeB合金以2000℃/s的预设升温速度在900~1100℃的温度范围内分别进行8min的电场烧结,并对烧结体的显微结构进行了研究。研究发现,随着烧结温度的升高,NdFeB合金烧结坯体的致密性逐渐提高。当烧结温度升至1050℃时,富Nd相细小、弥散、分布均匀,并显示出比传统方法烧结磁体更为优良的显微结构。随着烧结温度的继续上升,富Nd相出现明显的聚集,烧结体中逐渐出现粗大的枝晶状α-Fe。结果表明,当NdFeB合金以2000℃/s的预设升温速度进行电场烧结时,其最佳烧结温度为1050℃,此时烧结体的磁能积为249kJ/m3。 相似文献
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纯三元NdFeB磁体的显微组织主要由Nd_2Fe_(14)B硬磁ψ相,富硼Nd_(1+ε)Fe_4B_4η相,富Nd相及少量杂相组成。其中占磁体体积百分比85%~90%的ψ相是非内禀磁特性的主要贡献者;占磁体体积5%的η相对iHc无益,但少许η相仍有利于ψ相形成,富Nd相对ψ相具包裹作用,有助于提高矫顽力;杂相使反磁化畴易于形成,应尽量少。同时,讨论了各显微组织的形成及作用机理。 相似文献
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ZHOU Shouzeng ZHANG Jin MA Deqing GAO Maolin University of Science Technology Beijing Beijing China 《金属学报(英文版)》1992,5(11):351-356
The magnetic properties,microstructure and magnetic hardening of sintered(Nd_(1-x)Dy_x)_(16)Fe_(77.2)B_(6.8) and Nd_(16)Fe_(77.2)B_(6.8)+ywt-%Dy_2O_3 magnets have been stud-ied.As an addition of Dy to the magnet during smelting,Dy atoms may enter thematrix phase Nd_2Fe_(14)B,so as to enhance H_A,refine grains and improve boundary struc-ture,as well as to increase H_(ci)of the magnet.If Dy_2O_3 is added to powder materialprior to sintering,Dy atoms diffuse into the epitaxial layer of grains of matrix phasecausing enhancement of K′_1,also refinement of grains and improvement of boundarystructure.The NdFeB based permanent magnets with higher H_(ci) and greater(BH)_mmay be produced by adding about 2—3 wt-% Dy_2O_3 which make a favourable conditionfor lower cost. 相似文献
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ZHOU Shouzeng TANG Weizhong WANG Run University of Science Technology Beijing Beijing China 《金属学报(英文版)》1991,4(7):59-63
The boundary microstructure of sintered alloy Nd_(15.5)Fe_(77)B_-(7.5) has been studied by TEM,AESand SAED.The boundary structure may be distinguished into 4 types.The first three typesremain the same during annealing,and the fourth changes its microstructure remarkably.The4th type is composed of two different regions,i.e.,the central Nd-rich phase and the epitaxiallaver of the Nd_2Fe_(14)B grains.Owing to the atomic diffusion and other types of mass trans-port,magnetic hardening occurred in the epitaxial layer,thus the coercivity of the alloy hasbeen improved. 相似文献
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SONG Xiaoping WANG Xiaotian HUANG Qihua LIU Junhai YAO Yinliang Xi''''an Jiaotong University Xi''''an China 《金属学报(英文版)》1992,5(8):123-127
An addition of Nb up to 2 at.-% into(Nd,Dy)-(Fe,Co)-B alloy causes the formation ofdendrite Fe_2Nb and the precipitates in hard magnetic grains.Both increases withincreasing Nb content.During sintering,part of Fe_2Nb dissolves within the 2:14:1 grains,and the Fe_2Nb along grain boundaries hinders the growth of 2:14:1 grains.During an-nealing,the dissolved Nb in(?)-phase precipitates out,and this nearby the grain boundarydiffuses into Nd-rich phase to form new granular Fe_2Nb and to increase the Nb contentin Nd-rich phase,this results in a precipitate-free zone in the(?)-grain near Nd-rich phase. 相似文献
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J.Q. Zhou M.G. Zhang 《金属学报(英文版)》2005,18(4):557-560
Alloy modification, accompanying with proper heat treatment, is commonly used to improve the thermal stability of NdFeB magnet. Traditional alloy modification is performed through melting process with alloy elements to form the multi-alloy. In doing so, these alloy elements not only are introduced into the inter-ranular boundaries, but partly into the main phase, thus decreasing to some extent the magnetism of the main phase. In this paper, the blending method is used to prepare the Nd22Fe71B7/Mo sintered magnet, and its magnetic properties and microstractures are investigated. The results show that by adding 1.5% (mass fraction) Mo, the intrinsic coercivity 24, of the magnet reaches the maximum value of 1719.36KA/m, while continually increasing the amount of Mo has a less effect on iHc Microstructures analysis indicates that Mo-free Nd-Fe-B magnet has not uniform grains in size, while that with Mo element has uniform grains in size and smooth grain boundaries. Experiments show that after the NdFeB magnet is sintered at 1273K and annealed at 873K, the added Mo element could prevent the equilibrium transformation between the main phase and Nd-rich phase, thus resulting in the precipitation of fine second main phase (Nd2Fe14-xMoxB) from the main phase boundaries, preventing the nucleation and expansion of anti-magnetic domain, and enhancing the coercivity. 相似文献
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混合合金法添加Ga对Nd—Dy—Fe—Co—B烧结磁体的磁性和微观结构的影响 总被引:2,自引:0,他引:2
对用混合合金法制备的Nd7.69Dy6.62Fe64.33Co14.83B6.53/Ga烧结磁体的磁性和微观结构进行了研究。结果表明:添加0.5%(质量分数)的Ga后;磁体的iHc由1232kA/m升高到1819kA/m,在200℃放置0.5h后的磁通不可逆损失由33.3%下降到5%以下,当Ga的添加量达到1.0%左右时,Ga的作用达到最大值,微观结构分析表明,不添加Ga磁体的晶粒边界,尤其是晶界角隅处多呈现弯曲和凹凸不平的形状,添加Ga磁体的晶粒边界则呈现平滑和近似直线的形状,烧结过程中Ga原子置换Nd2Fe14B相中Fe原子形成Nd2Fe14-xGaxB相,与此同时,被置换的Fe原子进入液相与富和Nd相、富B相反应形成新的Nd2Fe14B(或Nd2Fe14-xGaxB)相,这是导致磁体的磁性和微观结构发生变化的主要原因。 相似文献