基于原位中子散射技术的铁镓智能材料力磁耦合行为机理研究

The rare-earth-free iron-gallium alloys (known as Galfenol) possess large magnetostriction effect, in combination with high mechanical strength, good ductility, and low saturating fields, which have many potential applications in joint military-civilian technique fields of importance. The study on inherent mechanism of magnetomechanical coupling behavior for iron-gallium alloys will show crucial significance on facilitating device design and practice use, and developing new-type smart materials. Neutron scattering is both the bulk and magnetic probe, which is the powerful tool for in situ investigation on microstructure evolution inside the bulk magnetic materials and the mechanism of relative physical effects. In the present project, the in situ neutron stress scanning technique will be employed to directly acquire the lattice strain response and distribution for each phase in the bulk and multiphase iron-gallium alloys under magnetomechanical environmental conditions. Meanwhile, the in situ small angle neutron scattering technique will be utilized to quantitatively obtain shape, size and distribution of the structurally heterogeneous phase in matrix, as well as the magnetic domain evolution under magnetomechanical loadings. Through our effort in the present project, from two length scales of the atom (lattice) and nanometer (magnetic microstructure), by the in situ study under magnetomechanical loadings for iron-gallium alloys with two compositions corresponding to dual magnetostriction peaks, the physical origin of large magnetostriction effect will be further clarified, and quantitative understanding on the mechanism of magnetomechanical coupling behavior in iron-gallium smart materials will be realized. The expected research results will give helpful guides on the construction of quantitative model for describing magnetomechanical coupling behavior for iron-gallium alloys, and provide some enlightenment in the development of high performance and multifunction for magnetostrictive smart materials.

铁镓智能材料兼具大磁致伸缩效应与良好力学性能，在军民两用重要技术领域具有广阔的应用前景。研究其力磁耦合行为的内在机理，对促进器件设计与实际应用、开发新型智能材料具有重要意义。中子兼具磁性与体探针的特性，是原位研究块体磁性材料中微观结构演化及相关物理效应机理的有力工具。本项目拟采用原位中子应力扫描技术，直接获取块体、多相铁镓合金在力磁耦合环境条件下各相的应变响应过程与分配规律；采用原位中子小角散射技术，定量获得力磁耦合加载条件下基体相中结构异质相的形状、大小、分布及磁畴演化。通过本项目从原子(点阵)及纳米(磁微结构)两个长度尺度，对磁致伸缩双峰成分点的铁镓合金在力磁耦合加载条件下的原位研究，可进一步阐明大磁致伸缩效应的物理本质，并实现对铁镓智能材料力磁耦合行为机理的定量理解。本项目预期取得的研究结果有助于构建描述铁镓合金力磁耦合行为的量化模型，并促进磁致伸缩智能材料的高性能与多功能化探索。

铁镓智能材料兼具大磁致伸缩效应与良好力学性能，在军民两用重要技术领域具有广阔的应用前景。研究其力磁耦合行为的内在机理，对促进器件设计与实际应用、开发新型智能材料具有重要意义。中子兼具磁性与体探针的特性，是原位研究块体磁性材料中微观结构演化及相关物理效应机理的有力工具。项目主要以两个大磁致伸缩成分点铁镓合金为研究对象，期望采用原位中子表征获取室温条件下合金微观结构、应力并与宏观行为进行关联，进而揭示大磁致伸缩的可能机制。首先针对铁镓及类似磁弹合金体系力-磁耦合行为机理关键科学问题，依托CMRR中子科学平台创新构建出原位力-磁耦合加载、衍射-声发射多探针以及原位磁场下多样品自动测量等系列技术，为磁弹合金及其它材料研究提供创新工具和多种综合实验表征平台。基于建立的原位力-磁耦合加载等实验技术，综合冷、热中子探针表征，获得典型成分铁镓合金在室温力-磁耦合作用下点阵应变以及内部磁畴及纳米尺度微观结构演化数据，揭示出两种典型成分铁镓合金内部纳米尺度微观结构分布差异性，从原子（点阵）和纳米尺度上丰富了磁致应变响应机制认识。譬如，基于原位中子表征已初步揭示出铁镓合金磁弹性能与内部纳米尺度结构有密切联系；但两种典型成分合金内部纳米尺度微结构（如尺寸分布和交换作用长度等）存在差异尚不清晰。因此，纳米结构演变及其对磁致应变的作用机制仍值得进一步深入研究。基于已获取研究认识，从纳米、畴和相等微结构层次已实现部分铁镓合金和相近体系材料的性能调控，通过微观结构控制得到性能优化的合金材料（如通过纳米结构实现磁致伸缩增强），为后续高性能新型材料设计开发和多功能化探索提供了指导思路。