ANISOTROPIC THERMAL EXPANSION AND FRACTURE OF RADIALLY ORIENTED TOROIDS OF RE-Co PERMANENT MAGNETS

研究SmCo_5辐向取向烧结环体的断裂机制指出:SmCo_5的强烈各向异性的热膨胀性质决定了辐向环在烧结后的断裂。导出了一个临界断裂取向度的表示式。计算和实验的结果都表明:烧结的SmCo_5辐向环的取向度通常不能大于0.7。实验发现以铜取代部分的钴,以及成分移向富钴的2-17相区,都使热膨胀各向异性特性明显降低,特别是Sm(Co_(0.80)Cu_(0.14)Fe_(0.06)_7和Sm(Co_(0.87)Cu_(0.13)_8二者几乎是完全各向同性的,是制备高性能辐向磁体的理想材料。还讨论了热膨胀各向异性的来源,在Sm(Co,Cu)_5中,铜原子可能部分地优先取代2c晶位。     

稀土钴永磁合金的各向异性热膨胀性质及辐向取向环体的断裂

研究SmCo_5辐向取向烧结环体的断裂机制指出:SmCo_5的强烈各向异性的热膨胀性质决定了辐向环在烧结后的断裂。导出了一个临界断裂取向度的表示式。计算和实验的结果都表明:烧结的SmCo_5辐向环的取向度通常不能大于0.7。实验发现以铜取代部分的钴,以及成分移向富钴的2-17相区,都使热膨胀各向异性特性明显降低,特别是Sm(Co_(0.80)Cu_(0.14)Fe_(0.06)_7和Sm(Co_(0.87)Cu_(0.13)_8二者几乎是完全各向同性的,是制备高性能辐向磁体的理想材料。还讨论了热膨胀各向异性的来源,在Sm(Co,Cu)_5中,铜原子可能部分地优先取代2c晶位。     

EFFECTS OF AS-CAST CRYSTALLINE STRUCTURE AND Cu SEGREGATION ON COERCIVITY OF Sm (Co, Cu, Fe, Mn)_(7.8) PERMANENT MAGNET

本文研究了Sm(Co, Cu, Fe, Mn)_(7.8)永磁体铸造结晶组织及Cu偏析对矫顽力的影响。结果表明,不同冷却速度的铸造合金锭具有不同的结晶组织。在等轴晶组织中,晶内贫Cu,晶界上富集游离Cu,保存有一些Sm_2Co_(17-x)T_x六方结构高温相,造成矫顽力下降;而在细的柱状晶组织中,无严重的成分偏析。经烧结和固溶处理后的磁体,为位错胞状显微组织,胞壁间弥散着脱溶Cu和富Cu的SmCo_(5-x)T_x相,它们在反磁化过程中,可能对畴壁起着钉扎作用,因而具有高矫顽力。     

Sm(Co, Cu, Fe, Mn)_(7.8)永磁体铸造结晶组织及Cu偏析对矫顽力的影响

本文研究了Sm(Co, Cu, Fe, Mn)_(7.8)永磁体铸造结晶组织及Cu偏析对矫顽力的影响。结果表明,不同冷却速度的铸造合金锭具有不同的结晶组织。在等轴晶组织中,晶内贫Cu,晶界上富集游离Cu,保存有一些Sm_2Co_(17-x)T_x六方结构高温相,造成矫顽力下降;而在细的柱状晶组织中,无严重的成分偏析。经烧结和固溶处理后的磁体,为位错胞状显微组织,胞壁间弥散着脱溶Cu和富Cu的SmCo_(5-x)T_x相,它们在反磁化过程中,可能对畴壁起着钉扎作用,因而具有高矫顽力。     

晶界添加MgO/Mg纳米粉对烧结钕铁硼磁性和抗腐蚀性的影响

为了提高烧结Nd-Fe-B磁体的磁性能和抗腐蚀性能,采用二元合金法,通过晶界添加MgO/Mg纳米粉烧结成(PrNd)_(15.5)B_6Cu_(0.1)Fe_(bal)Mg_x(x=0.1～0.3,质量分数,%)永磁体。利用永磁特性自动测量仪、扫描电子显微镜、X射线衍射仪和CHI660E电化学工作站对不同添加量的MgO/Mg(质量比为1:2)纳米粉的烧结Nd-Fe-B磁体的磁性能、微观结构及抗腐蚀性能进行了研究。结果表明:当MgO/Mg纳米粉添加量为0.1%时,磁体综合磁性能表现最好,此时磁体矫顽力1183 kA/m,剩磁1.22 T,最大磁能积288 kJ/m~3。由塔菲尔曲线可知,随着MgO/Mg纳米粉添加量的增多,腐蚀电位从–1.093 V提高到–0.929 V;腐蚀电流密度从223.87μA/cm~2降低到42.66μA/cm~2;由电化学阻抗谱图可知,添加了适量的MgO/Mg纳米粉的磁体的高频容抗弧的半径大于未添加磁体的高频容抗弧的半径,增大了电荷迁移阻力。因此晶界添加适量的MgO/Mg纳米粉提高了烧结Nd-Fe-B磁体的磁性能和抗腐蚀性能。     

AlN纳米粉晶界添加对烧结Nd-Fe-B磁体耐腐蚀性能的影响

研究AlN纳米粉的晶界添加对烧结钕铁硼磁体显微结构、耐腐蚀性能及磁性能的影响。结果表明,AlN纳米粉的晶界添加可以有效提高磁体的耐腐蚀性能,当添加量为0.1%(质量分数)时,耐腐蚀性能最佳。同时,其添加也可以提高磁体的矫顽力。显微组织观察表明,纳米AlN的晶界添加有效细化了磁体主相的晶粒,这是耐腐蚀性能和矫顽力同时提高的主要原因     

简讯

高钴含量Nd(Pr)-Dy-Fe-Co-B磁体烧结特点俄罗斯航空材料研究院А.Ф.ПЕТРАКОВ等人研究了钴含量对Nd(Pr)-Dy-Fe-Co-B磁体烧结温度的影响。对于(Nd1-xDyx)13～17(Fe1-yCoy)余量B5～9(x=0.06～0.71;y=0.02～0.34)磁体,达到99%最高密度的烧结温度Tcn1随Co量增高线性降低。达到Hci最高值的烧结温度Tcn2总是低于Tcn1。烧结时形成液相的主要成分为(Nd,Dy)(Fe,Co)2和(Nd,Dy)(Fe,Co)4B。对于(Pr1-xDyx)12～17(Fe1-yCoy)余量B6～8(x=0.18～0.48;y=0.15～0.47)磁体,当y≈0.26时,烧结温度Tcn1最     

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

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。     

纳米晶SmCo_(8.9)Si_(0.9)永磁合金相变特征及其磁性能变化研究

首次制备出具有高稳定性的Sm Co_(8.9)Si_(0.9)纳米晶合金,进而系统研究了亚稳相Sm Co_(8.9)Si_(0.9)的相变特征及相应的磁性能变化规律。发现添加元素Si可以有效提高过饱和固溶体亚稳相SmCo_(9.8)的稳定性,随着热处理温度的升高,SmCo_(8.9)Si_(0.9)纳米晶合金由SmCo_(9.8)(H)结构的单相转变为Sm_2Co_(17)(H)和Co(fcc)相,且伴随相变,矫顽力提高。其机理源于析出的细小Co相造成钉扎机制增强。进一步升高热处理温度,Sm_2Co_(17)(H)相转变为Sm_2Co_(17)(R)相,同时晶粒长大明显且晶粒尺寸分布不均匀,导致磁性能下降。     

添加Dy2O3对烧结NdFeB磁体微观结构的影响

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。     

放电等离子烧结-热变形各向异性Nd-Fe-B磁体的微观组织及磁性能

采用放电等离子烧结及后续热变形技术制备各向异性Nd-Fe-B磁体,研究烧结温度对放电等离子烧结Nd-Fe-B磁体微观组织和磁性能的影响。随着烧结温度在650~900°C范围内的升高,烧结态Nd-Fe-B磁体的剩磁、内禀矫顽力及最大磁能积呈现先升后降的趋势。在800°C下烧结所获得磁体的磁性能最佳。随后,对800°C烧结后具有最佳磁性能的磁体采用放电等离子烧结技术进行后续热变形处理。与初始吸氢-歧化-脱氢-再复合粉末和烧结态磁体相比,热变形磁体拥有更显著的各向异性和更好的磁性能。当热变形温度为800°C且压缩比为50%时,热变形磁体中的Nd2Fe14B晶粒呈扁平片状且不发生异常长大;磁体沿热压方向具有最佳的磁性能：Br、Hcj和（BH）max分别为1.16 T、449 k A/m和178 k J/m3。     

Microstructure of Sm2Co17 magnets and its influence on coercivity

Sm(CobklFe0.197Cu0.049Zr0.026)7.5 magnet with Hci of 2105 kA/m and β18-200℃ of - 0.17 % /℃ was made by sintering processing. The magnet has uniform celluler structure. The cell interior is a rhombohedarl 2 : 17 phase,and the boundary is a hexagonal 1 : 5 phase. The average cell size is 93 nm and the cell boundary thickness is 20 nm.The cells are enriched in Fe, and the cell boundaries are enriched in Cu. More Cu-riched 1 : 5 cell boundary phase would be helpful to obtain a higher coercivity and lower temperature coefficient. White secondary phase mainly consisting of Sm can decrease the coercivity of the magnets, but the closely paralleled grooves can increase coercivity.     

Microstructures and magnetic properties of Ce32.15Co49.36Cu9.84Fe9.65 magnet sintered at different temperatures

The microstructures and magnetic properties of Ce32.15Co49.36Cu9.84Fe9.65 magnet sintered at the temperatures ranging from 1005 to 1105 ℃ were investigated.The results on scanning electron microscopy and X-ray diffraction analysis indicate that the remanence Br of the magnets is mainly influenced by the degree of the easy-axis orientation when sintering temperature is less than 1085 ℃,the rapidly increasing amount of the secondly phase (5∶19 phase) gives rise to the deterioration of the magnetic properties of the magnet above 1085 ℃.Moreover,it is found that intrinsic coercivity Hci is strongly related to the content of copper in the matrix of the sintered magnets.The optimal sintering temperature is located in 1025～1055 ℃,the corresponding magnetic properties of the magnets are Br=0.685 T,Hci=350 kA·m-1,and maximum energy product (BH)m=85.6 kJ.m-3.     

Structure and magnetic properties ofhigh-performanced Sm2（Co, Fe, Cu, Zr）17 alloys

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烧结NdFeB磁体热压变形后富Nd相的显微组织

采用热压变形法对NdFeB磁体晶间富Nd相的显微组织进行了研究,实验结果表明,NdFeB磁体经真空热压变形后,富Nd相不再平均地分布在磁体晶间,而是聚集成团块状或从磁体边缘渗出,显微组织分析表明,富Nd相主要是由α-Dd和Nd2Fe17两相组成,与Nd-Fe合金的共晶组织成分接近,对于晶间添加Al元素的磁体,Al溶入晶间形成Nd2Fe15Al2相弥散地分布在晶界上,这有益于磁体矫顽力的提高;对于晶间添加Cu元素的磁体,晶间没有发现有新相产生。     

SPS制备SmCo7-xFex块状纳米晶磁体的研究

采用高能球磨法制得SmCo7-xFex非晶粉末,然后采用放电等离子技术将其烧结为块状纳米晶磁体,对磁体的微观结构和磁性能进行了观察和测试.结果表明,SmCo7-xFex球磨5 h后成为非晶粉末,经SPS烧结后得到1:7相.TEM观察表明,磁体晶粒尺寸在20～50 nm.另外,磁体具有较好的磁性能,当x=0.4时,矫顽力为992.8 kA/m,剩磁为0.634T,(BH)max为69.75KJ/m3.     

高密度块状钐铁氮磁体制备的研究进展

钐铁氮化合物(Sm₂Fe₁₇N₃)因具有比钕铁硼(Nd₂Fe₁₄B)更高的磁晶各向异性场和居里温度值及更少的稀土含量,成为新型稀土永磁材料研究热点。但是,由于钐铁氮在600℃左右会分解导致永磁性能消失,因此常规的高温烧结工艺并不适用于钐铁氮烧结磁体的制备,现只能将其与高分子材料复合用作塑磁材料,这就导致Sm₂Fe₁₇N₃的磁学性能无法得到充分发挥。因此,开发低温成型工艺制备全金属高密度块状磁体是获取高性能钐铁氮磁体的关键。经过30多年的努力,科研人员已开发出多种制备钐铁氮磁体的低温快速成型工艺,并获得最大磁能积达到199 k J/m³的高性能磁体。本研究将从磁体的制备方法出发,总结当前块状钐铁氮磁体的研究现状及面临的问题,尤其针对不同成型方法出现矫顽力下降的现象提出分析,并对其今后的发展做出展望。     

放电等离子烧结NdFeB磁体的富稀土相与矫顽力

利用放电等离子烧结技术(SPS)制备新型烧结磁体SPS NdFeB。为了更好理解磁体的磁性能,尤其是矫顽力和微组织关系的机理,本研究以热处理前后的SPS NdFeB为研究对象,利用扫描电镜(SEM)、高分辨透射电镜(HRTEM)、X射线能谱仪,B-H回线仪分别对磁体的显微组织和高分辨透射电镜像组织和磁性能进行了系统研究。结果表明,经过热处理后,磁体矫顽力明显提高,富稀土相的铁原子与稀土原子比Fe/Re明显下降;富稀土相结构形态发生明显变化,由热处理前的非晶态变为热处理后的晶态。     

Effect of Fe on Microstructure and Coercivity of SmCo-Based MagnetsEI北大核心CSCD

High-temperature permanent magnets have an important application in the aerospace and other high-tech fields, among which 2:17-type SmCo magnets have become the first choice for high-temperature permanent magnets due to the strong magnetic anisotropy and high Curie temperature. Although there are studies on the effect of Fe on the remanence and coercivity, the role that Fe plays on coercivity mechanism of SmCo magnets is still unclear. In this work, Sm(CobalFexCu0.08-0.10Zr0.03-0.033) z (x= 0.10-0.16, z=6.90 and 7.40) magnets are prepared and the magnetic properties under different temperatures are investigated. The magnets with an intrinsic coercivity of 603.99 kA/m and a maximum energy product of 87.30 kJ/m(3) at 500 degrees C. are obtained. It is revealed that at room temperature the coercivity of the magnets increases with increasing Fe content, however, at 500 degrees C. the coercivity shows an opposite dependency on Fe content. Moreover, the effect of Fe on coercivity is more obvious at low z value. The phase structure and composition analyses were characterized by XRD and TEM. The results show that with the increase of Fe content, the size of the 2: 17R cell phase increases, the volume ratio of cell boundary 1: 5H phase decreases, and furthermore, both Fe content in the 2: 17R phase and Cu content in the 1: 5H phase increase. The variations of Fe and Cu contents in both phases lead to the change of the domain wall energy difference. With the increase of Cu content of 1:5H phase, the domain wall energy of 1: 5H phase (gamma(1:6)) drops faster at room temperature, the coercivity is determined by gamma(2:17)-gamma(1:5), so the coercivity increases with increasing Fe content. While at 500 degrees C, due to gamma(1:6) at its Curie temperature, the coercivity is mainly determined by the domain wall energy of 2: 17R phase (gamma(1:17)), which decreases with increasing Fe content. The increase of Fe content at the low z value results in a smaller growth of cell size, which leads to a more significant change in coercivity.