论文编号:CL003 论文字数:22379,页数:35
摘 要
超磁致伸缩材料作为一种新型功能材料，受到世界高技术领域专家们的极大关注，发展迅速。美国、日本等国家对其制备工艺、成分、相结构、磁结构和性能做了大量研究工作，技术已经日趋成熟。但是稀土超磁致伸缩材料是铁磁导电物质，当外加磁场强度变化时，将在介质中产生涡流，使材料发热，而且交变磁场频率越高，涡流越强烈，从而限制了磁致伸缩材料在超声技术中的应用。树脂基稀土超磁致伸缩复合材料（Giant Magnetostrictive Powder Composite，GMPC）的出现，解决了这个问题。其上限频率可达100kHz，这就大大扩充了超磁致伸缩材料在高频超声技术中的应用，具有极大的发展前景。
本论文旨在：（1）设计、研制一套适用于GMPC的制备成型模具，包括磁场的施加措施等；（2）采用手工破碎制粉技术和自行设计的成型模具、用粉末粘结法制备出性能良好的GMPC，对其磁致伸缩、电阻等性能进行综合测试分析；（3）研究GMPC的磁场成型工艺对其磁性能的影响规律，从而探索出GMPC的最佳制备工艺。
实验采用D8-ADVANCE型X射线衍射仪进行材料结构及物相分析，用JSM-5610LV型扫描电镜观察样品组织及颗粒表面形貌，用4×BⅡ型（双目）金相显微镜观察试样的金相显微组织，采用OMEC SCF-106型激光粒度分析仪测试粉体的粒度，采用TG328A型分析天平测量合金和复合材料的密度，用Aglient4294A型动态阻抗分析仪测量GMPC的动态电阻率，采用直流电桥电阻应变片法测量样品的磁致伸缩系数。
实验得到如下结论：（1）采用非自耗电弧炉熔炼-烧铸技术，通过控制热流方向，制备出较高性能的稀土超磁致伸缩合金。实验表明，所制备的合金棒具有明显的Laves相结构的ReFe2相，合金组织均匀，且具有一定的择优生长，磁致伸缩量在本实验条件下最大可达782×10-6，是较理想的磁致伸缩合金；（2）采用手工破碎制粉技术和自行设计的成型模具、用粉末粘结法能够制备性能良好的GMPC。所制备得的GMPC最大磁致伸缩量λm最高可达491.3×10-6，与原材料Terfenol-D的磁致伸缩量（近705.6×10-6）相比，λm只降低了约30％；（3）在其它制备工艺条件相同时，经磁场成型的GMPC其λm(最大磁场为400kA/m下的磁致伸缩)为491.3×10-6，而未经磁场成型的λm为402.6×10-6，说明在磁场下成型可以使晶粒有很好的定向，从而提高了复合材料的磁致伸缩性能；（4）GMPC电阻率测量结果表明，所制备的样品电阻率约为32×10-2Ω·m，比合金Terfenol-D的电阻率约大四个数量级，说明制备的GMPC将具有较好的高频磁性能，通过对GMPC组织形貌进行分析，发现GMPC组织均匀，很少有气孔，致密度很高。
另外，对掺Ho合金制备过程中出现的蘑菇进行了研究。从实验得到如下结论：（1）对掺Ho合金蘑菇析出物的研究发现：经退火处理后，随着Ho含量的增加，“蘑菇”状析出物越多，析出的“蘑菇”为多相组织，主要包括DyFe2相、RE(Tb,Dy)5Si3和稀土氧化物相，还存在少量其它杂质；（2）“蘑菇”的析出（过量稀土元素的析出），使得基体成分优化为Tb0.2234Dy0.678Ho0.354Fe2，从而具有较好的磁致伸缩性能，理论上，蘑菇的出现是由于能量最小化作用的结果；（3）随着Ho含量的增加，合金的磁致伸缩系数先减小，含量为0.15时，达最小值213.5×10-6，随后又渐渐升高，含量为0.25时， 达538.8×10-6。含量为0.25时，合金样品中析出的“蘑菇” 磁致伸缩系数最小，为114.2×10-6。
关键词：Terfenol-D；磁致伸缩；复合材料；制备；掺Ho；蘑菇
Abstract
As a novel functional material ,magnetostrictive material has risen comprehensive attention by the experts in the high-tech fields and got momentum in the past few years.Much work has done on the preparation ,composition ,phase structure ,magnetic-structure and properties in U.S.A ,Japan and so on ,which make the technology mature gradually .But as a ferromagnetic electric conductor, when the magnetic field changes,eddy that makes material heat will produce. And when the reversal frequency of magnetic field is higher, the eddy is violent,those defects limit its application in ultrasonic technology. The appearance of polymer-bonded giant magnetostrictive composite(GMPC) solved this bottle-neck.The effective frequency of GMPC can reach to 100KHz ,which greatly extended the application of magnetostrictive materials in ultrasonic technology .GMPC has great developmental prospects .
The main aims are:(1)a mould which applied to the fabrication of GMPC was designed and produced,the magnetic field was also considered;(2) excellent GMPC was fabricated with the technique of manual milling,mould,and powder felting, properties of magnetostriction,resistance and so on was also tested;(3)the magnetic properties which were influenced by the processing in the magnetic field were researched,the optimum technics was also explored.
The properties of GMM and GMPC were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), standard resistance strain gauge technique , VSM and so on in this paper.
The GMPC in this experiment was cured with GMM powder and resin under stress .We got optimum particle size of 112.5μm ,compaction pressure of 0.5GPa ,phenol content of 3.1～4wt%,and the direction of applied magnetic field according to the data essayes provided.The material was formed in that optimum condition.The results show as follows:(1)the GMM was fabricated by the technique of arc-melting-casting after controlling the direction of heat,result shows that the phase of the alloy was REFe2,struture was uniform and had some preferiation ,the maximum magnetostriction in the magnetic field provided in this experiment(λm) was 780×10-6 and turned to be ideal alloy;(2)the excellent GMPC was fabricated with the technique of manual milling,mould,and powder felting.λm was 491.3×10-6 which loses only 30% with respect to the magnetostriction of GMM(705.6×10-6 more or less);(3)the composites pressing in the magnetic field has the λm of 491.3×10-6 and those without 402.6×10-6,the composites pressing in the magnetic field have better property;(4)The gained composites are of uniform microstruture ,few air hole and high density,what’s more,resistance of the sample is about 32×10-2Ω·m which is four orders of magnitude larger than GMM reported.
The mushrooms that appeared in the processing of Ho dopping alloy were analysed ,which shows:(1)The alloy rods have the structure of obvious MgCu2 Laves cubic structure while mushrooms are phase of rare-earth oxidation ,RE(Tb,Dy)5Si3 and also Laves cubic;(2)the separating out of the mushroom(the seprating of excessive rare-earth elements) makes the component of Tb0.2234Dy0.678Ho0.354Fe2 which leads to good magnetostriction properties;in theory ,the appearing of the mushroom is the minimization of energy;(3)the magnetostriction of the alloy decreases with the increasing amount of Ho dopping,minimum occurs at x(ratio of Ho atom)=0.20 and increases gradually until x=0.25 with the magnetostriction of 538.8×10-6.
Key word: Terfenol-D; Magnetostriction; Composite;Ho dopping ;Mushroom
目 录
摘要
Abstract
1 绪论 1
1.1 引言 1
1.2 超磁致伸缩材料性能及其研究现状 1
1.2.1超磁致伸缩材料的性能特点 1
1.2.2超磁致伸缩复合材料的性能 2
1.2.3超磁致伸缩材料与超磁致伸缩复合材料综合性能比较 2
1.2.4超磁致伸缩材料的研究现状 3
1.2.4.1超磁致伸缩合金的研究现状 3
1.2.4.2超磁致伸缩复合材料的研究现状 3
1.3 稀土-铁系超磁致伸缩材料的制备技术 3
1.3.1“一步法”新工艺 3
1.3.2粉末冶金法 4
1.3.3薄膜制备技术 5
1.4 工艺参数的优化选择 5
1.4.1颗粒尺寸的选择 5
1.4.2成型压力的选择 6
1.4.3树脂含量的选择 6
1.4.4其它 6
1.5超磁致伸缩材料的应用 6
1.6 GMM应用市场分析 7
1.6.1国内外市场需求 7
1.6.2GMM的市场前景 8
1.7 本课题的研究内容及意义 8
2 实验准备工作 9
2.1 材料的准备 9
2.1.1合金的准备 9
2.1.2 树脂粘结剂主要成份的选择 9
2.1.2.1树脂的选择 9
2.1.2.2固化剂的选择 9
2.2模具的设计、研制 10
2.3 测试方法 12
2.3.1分析测试方法 12
2.3.2 磁致伸缩系数(λ)的测量 12
2.3.3 GMM和GMPC密度的测量 13
3 合金的制备 14
3.1 GMM制备 14
3.1.1合金制备 14
3.1.2合金的XRD分析 14
3.1.3合金的SEM分析 15
3.1.4合金的磁致伸缩系数 16
4 超磁致伸缩复合材料的制备及性能测试 17
4.1 GMPC制备 17
4.2 GMPC性能测试与结果讨论 17
4.2.1 GMM合金粉末粒度分析 17
4.2.2磁致伸缩常数的测量 18
4.2.3 组织形貌的观测 19
4.2.4合金和复合材料的密度测定结果 19
4.2.5复合材料的电阻率测定结果 19
4.3 关于GMPC制备的总结 20
5 掺Ho超磁致伸缩材料合金退火后“蘑菇”状析出物研究 21
5.1 掺Ho超磁致伸缩合金退火后“蘑菇”析出 21
5.2 基体棒和“蘑菇”分析 21
5.2.1组织形貌分析 21
5.2.2成分分析 22
5.2.3XRD物相及结构分析 23
5.3 磁致伸缩常数的测量 25
6 结论 22
谢辞 26
参考文献 27
超磁致伸缩复合材料的制备......