基于同步辐射技术的稀土掺杂Fe-Ga 快淬合金磁致伸缩机理研究

The novel Fe-Ga magnetostrictive alloys are becoming one of the most active research areas in magnetostrictive material field due to their higher mechanical strength, better toughness, larger low-field magnetostriction and lower associated cost in recent years. However, the magnetostrictive properties of the practically prepared polycrystalline Fe-Ga based alloys are quite small at present and the magnetostrictive mechanism is not very clear yet. The project proposes innovatively that the magnetostrictive property of the Fe-Ga based alloys are improved through the rare earth elements doping and quenching. The effects of the type of rare earth element doping, the content of rare earth element doping and quenching speed on the microstructures and the magnetostrictive properties of Fe-Ga alloy and its mechanism were investigated, respectively. On this basis, a good quenched Fe-Ga alloy doped with rare earth element is prepared by selecting the types of rare earth element and controlling of the content of rare earth element and quenching speed. The relationship of microstructures and magnetostrictive properties of Fe-Ga system alloys are clarified. In order to explore the magnetostrictive mechanism of quenched Fe-Ga alloy doped with rare earth element and the effects of the microstructures on the magnetostrictive properties of Fe-Ga alloy, the Lattice microstructures, including occupation of lattice site, local structure of certain atoms and disorder-order transition, and electronic structure of the typical quenched Fe-Ga alloy doped with rare earth element were investigated by means of XAFS. Possible approaches will also be proposed to enhance the magnerostrictive coefficient and improve the appliction of Fe-Ga alloys in this project.

新型Fe-Ga磁致伸缩合金以其高强度、良好韧性、低场高磁致伸缩性能和低成本等优势成为目前磁致伸缩材料领域的研究热点。然而实际制备的多晶Fe-Ga合金磁致伸缩系数并不高，且磁致伸缩机理仍不清楚。本项目创新性的提出通过稀土掺杂和快淬处理联合改善Fe-Ga合金的磁致伸缩性能，具体分别研究掺杂稀土元素种类、掺杂量以及快淬速度对Fe-Ga合金结构和性能的影响及其机理。并合理挑选和调控稀土元素种类、掺杂量以及快淬速度，制备磁致伸缩性能优良的快淬态稀土掺杂Fe-Ga合金，探索合金结构与性能的关系。为阐明快淬态稀土掺杂Fe-Ga合金磁致伸缩机理以及微结构对磁致伸缩性能的影响，创新性的采用同步辐射X射线吸收精细结构(XAFS)技术对典型快淬态稀土掺杂Fe-Ga合金的晶体微结构进行研究。本项目研究指明了提高Fe-Ga合金磁致伸缩系数的途径，促进Fe-Ga系合金的实用化研究。

新型Fe-Ga合金以其高强度、良好韧性、低场高磁致伸缩性能等优势而倍受关注。但实际制备多晶Fe-Ga合金磁致伸缩系数并不高，限制了其实际应用。项目以Fe83Ga17合金为研究对象，通过采用稀土掺杂、优化制备工艺、制备复合材料等方法，显著提高了Fe83Ga17合金的磁致伸缩性能，并揭示了性能提高的机理。同时将Fe-Ga合金扩展到Fe-Al合金进行稀土掺杂。通过项目实施，取得了以下主要成果：1）对不同种类稀土掺杂研究中发现，稀土Ce，Sm和Y掺杂Fe-Ga合金，几乎无稀土元素进入A2晶格。合金中形成(001)取向柱状晶的含量是影响其磁致伸缩系数的主要因素。而稀土La，Pr和Nd掺杂Fe-Ga合金，有部分稀土元素进入A2晶格，导致A2晶格膨胀，产生畸变，这是影响其磁致伸缩系数的主要因素。2）对不同稀土掺杂量研究中发现，仅有微量稀土（掺杂量≤1.0 at%）掺杂才能有效改善Fe-Ga合金磁致伸缩性能。用0.6at%的Pr掺杂Fe83Ga17合金，其磁致伸缩系数可达192 ppm。与Fe83Ga17合金相比，其磁致伸缩系数增加了400 ％。3）采用第一性原理对Cu掺杂Fe-Ga合金进行研究发现，掺杂的Cu元素是间隙溶入到主相A2晶格中。Cu掺杂使得Fe-Ga合金的杨氏模量减小，这导致Fe83Ga17合金的磁致伸缩系数随Cu掺杂量的增加而减小。4）定向凝固是改善合金磁致伸缩性能的有效方法。当凝固速率为30 mm/min时，合金中有Fe6Ga5相形成，促进了合金的磁致伸缩性能。5）创新的制备了柔性稀土掺杂 Fe-Ga 磁致伸缩复合材料，获得了最大磁致伸缩系数为310 ppm的复合材料。6）各向异性大的稀土Tb掺杂Fe-Al合金的磁致伸缩性能更优于各向异性小的稀土La掺杂Fe-Al合金。项目研究结果为丰富和完善Fe基磁致伸缩材料具有重要的意义，也为提高Fe基磁致伸缩合金指明方向，促进其实用化研究。