微量稀土元素添加增强FeGa合金巨磁致伸缩效应的微观机制研究

As a kind of metallic functional materials, magnetostrictive alloys show important applications in aerospace, marine exploration, and petroleum extraction. FeGa alloys have the advantages such as low field induced large magnetostriction, high mechanical strength and low cost. Especially, we found that FeGa alloys doped with trace rare earth element La exhibit giant magnetostrictive effect comparable with that of TbDyFe, which are a new kind of giant magnetostrictive materials with important applications. . The previous studies indicate that nanoheterogeneities are responsible for the large magnetostriction in FeGa, while the microscopic mechanism on the giant magnetostriction in FeGa alloys induced by trace rare-earth element addition needs to be further studied in detail. This project intends to investigate the occupied position as well as the interaction between rare earth element and nanoheterogeneities, including 1) the microstructure, magnetic properties, and magnetostriction of trace La doped FeGa alloys with nanoheterogeneities of different volume ratio, 2) the microstructure, magnetic properties and magnetostriction of FeGa alloys after La precipitates out via heat treatment. The purpose is to reveal the microscopic mechanism of the trace rare earth element induced giant magnetostriction in FeGa alloys, providing the theoretical basis for the application of this new kind of Fe-based giant magnetostrictive alloys.

磁致伸缩材料作为一类重要的金属功能材料，在航空航天、深海探测、石油开发等领域具有广泛的应用前景。FeGa合金具有低场大磁致伸缩、高力学性能、低成本等优点，特别是本课题组发现的微量稀土元素La强制固溶到FeGa合金中，磁致伸缩性能提高3倍以上，与价格昂贵的稀土巨磁致伸缩材料TbDyFe性能相当，是一种有重要应用价值的新型巨磁致伸缩材料。. FeGa合金大磁致伸缩源于纳米异质结构，微量稀土元素添加进一步增大磁致伸缩效应的微观机制需深入研究。本项目拟通过研究微量稀土元素的存在形式，及其与FeGa中纳米异质相的交互作用，包括微量La元素固溶在不同体积分数纳米异质相FeGa合金中其结构、磁性和磁致伸缩性能演变规律，以及La析出后，其结构、磁性和磁致伸缩性能变化，揭示微量稀土添加增强FeGa合金巨磁致伸缩效应的微观机制，为这一类新型铁基巨磁致伸缩材料实际应用奠定理论基础。

磁致伸缩材料作为一类重要的金属功能材料，在航空航天、深海探测、石油开发等领域具有广泛的应用前景。FeGa合金具有低场大磁致伸缩、高力学性能、低成本等优点，特别是本课题组发现的微量稀土元素La强制固溶到FeGa合金中，磁致伸缩性能提高3倍以上，与价格昂贵的稀土巨磁致伸缩材料TbDyFe性能相当，是一种有重要应用价值的新型巨磁致伸缩材料。然而，微量稀土强制固溶增强FeGa合金巨磁致伸缩效应的具体微观机制尚需深入研究。. 本项目针对微量稀土掺杂FeGa巨磁致伸缩合金，首先利用第一性原理计算形成能，发现微量稀土元素倾向于在纳米异质相而非基体中析出，且能产生更大的四方畸变，球差校正电镜高角度环形暗场像表明纳米异质结构在<100>方向具有择优取向，两者共同导致巨磁致伸缩效应；进而通过实验证实掺杂稀土元素与纳米异质相存在交互作用，无纳米相合金掺杂稀土后磁致伸缩效应基本不变，存在纳米异质相合金掺杂稀土后磁致伸缩效应大幅提高；进一步设计了高温热处理实验来调控大原子在基体中的固溶量，发现当稀土元素以第二相方式析出时，磁致伸缩性能显著降低，通过反证的方式确定了大原子Tb通过固溶进入纳米异质结构，产生巨磁致伸缩效应；最后我们拓展到具有复杂纳米析出相结构的高Ga含量FeGa合金中，通过微观结构研究解释了其磁致伸缩性能的演变。该研究为开发新型巨磁致伸缩材料并实现其在航天领域的应用奠定了理论基础。