大块纳米晶马氏体NiTi合金的弹性变形行为研究

The physical and chemical properties of crystal materials are close related to their elastic strain. The ultra-large elastic strain (lattice strain) of crystal materials may bring in Various properties (elastic strain engineering). However, the ultra-large elastic strain of bulk metals has been proved to be difficult, which limited their applications. Based on the preliminary exploration, we found that the maximum elastic strain (lattice strain) of the nanocrystalline martensitic NiTi alloy is up to 4.8%, which corresponds to the elastic strain of nanowires. It was also found that， after unloading, the alloy reserves a large tensile strain (about 1%), and the macroscopic strain of the alloy is much larger than the microscopic strain upon the loading-unloading cycle (a difference of about 2%). It is proposed that these phenomena are close related to the microstructure and elastic/plastic deformation of the nanocrystalline martensitic NiTi alloy. This project intends to reveal the effects of microstructure and elastic/plastic deformation micro-mechanisms on the macro/micro-elasticity of the alloys, and to clarify micro-mechanisms of the phenomena descript above. It is expected to obtain high-quality academic achievement.

晶体材料的物理及化学性能与其弹性应变密切相关，通过获得超大弹性应变（晶格应变）可望实现人们所需的各种功能特性，即弹性应变工程。然而，现有报道仍未能实现大块晶体材料的超大弹性应变。在前期研究中，我们发现大块纳米晶马氏体NiTi合金在拉伸方向的最大弹性应变（晶格应变）高达4.8%，与自由态纳米线的弹性应变极限相当；且卸载后保留了较大微观拉应变（约1%）；并发现其宏观弹性应变远大于可回复晶格应变（相差约2%）。我们猜测合金的以上特征与其微观结构及弹、塑性变形机制密切相关。本项目结合同步辐射原位技术与TEM观察，拟揭示纳米晶马氏体NiTi合金的微观结构及弹、塑性变形机制对其宏、微观弹性的影响，进而揭示其呈现上述特性的微观机制，可望获得高质量学术成果。

项目旨在揭示大块纳米晶马氏体NiTi合金超大弹性变形的内在机制。研究了纳米级马氏体NiTi合金发生超大弹性应变的机制，探索了纳米晶马氏体NiTi合金加载过程中的塑性变形机制及微观可回复变形机制，分析了晶粒尺寸对纳米晶马氏体NiTi合金弹、塑性变形的影响。此外，项目进一步拓展设计、制备了多种成分的V纳米线增强NiTiV复合材料，并初步研究了复合材料的相变及力学性能。通过该项目的研究，负责人以第一及通讯作者共发表论文7篇，其中SCI论文6篇，EI论文1篇；并申请中国发明专利4项，其中授权1项。完成了课题计划任务和预计的成果。