点阵切变基体中纳米线超大弹性变形的特征与机制

项目名称： 点阵切变基体中纳米线超大弹性变形的特征与机制

项目编号： No.11474362

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 数理科学和化学

项目作者： 崔立山

作者单位： 中国石油大学（北京）

项目金额： 86万元

中文摘要： 单体态纳米线具有超大弹性应变（4-7%）/超高屈服强度，然而，其在大块复合材料中却失去此性能，此超常力学性能未能从纳米走向宏观 现象被喻为死亡之谷。在前期研究中，我们一改以往文献中选择的常规金属基体（位错滑移塑性变形机制），选择以点阵切变为变形机制的NiTi记忆合金为基体，实现了宏观复合材料中纳米线呈现超大弹性应变（4-7%），跨越了死亡之谷。并初步发现，此基体中纳米线的超大弹性变形呈现瞬时性、局域性及应变分布不均匀性等特征；并当基体切变应变过与欠匹配于纳米线弹性应变时，纳米线呈现不同的超大弹性变形特征；且通过预拉伸处理可使自由态（无外载）复合材料中纳米线保持大弹性应变。本项目拟揭示纳米线呈现超大弹性应变的特征与机制，阐明其超大弹性变形与基体点阵切变变形之间的内在联系，澄清自由态复合材料中纳米线保持大弹性应变的特征与机制，为高性能纳米线复合材料的设计与应用奠定理论基础。

中文关键词： 纳米线；点阵切变；形状记忆合金；复合材料；超大弹性应变

英文摘要： Freestanding nanowires often have ultrahigh elastic strain limits(4-7%), but exploiting their intrinsic mechanical properties in bulk composites has proven to be difficult. That the exceptional properties not going from nano to macro has commonly been dubbed the Valley of Death. In our preliminary study, we have realised the ultra-large elastic strain (4-7%) of Nb nanowires in a bulk composite, and crossed the Valley of Death. This breakthrough is accomplished by selecting a NiTi shape memory alloy as matrix instead of the conventional metals which is commonly used. The deformation mechanisms are totally different between these two matrix with the former deforms primarily by lattice shear and the latter by dislocation slip after an initial elastic deformation. Meanwhile, we found that the nanowires show the behaviors of instantaneous and local change of strain and inhomogeneious distribution of strain during their ultra-large elastic deformation. Also, the ultra-large elastic behaviors of nanowires are different when the shear strain of matrix is larger or smaller than the elastic strain of nanowires. By a pre-treatment, the large elastic strain of nanowires in the composite can be retained even after moving the external load. The project intends to reveal the characteristics and mechanisms of ultra-large elastic strain of the nanowires in a NiTi matrix, illustrate the relationship between the ultra-large elastic deformation of nanowires and the lattice shear deformation of matrix, and clarify the characteristics and mechanisms of retaining large elastic strain of the nanowires in the bulk composite without external load. This will lay a theoretical foundation for the development of high-performance composite reinforced by nanowires.

英文关键词： nanowires;lattice shear;shape memory alloy;composite;ultra-large elastic strain