点阵切变基体中颗粒的弹性变形行为研究

Elastic strain of reinforcements (particles, nanowires) is closely related to the mechanical properties of composites, but the elastic strain of reinforcements is smaller in composites. For example, freestanding nanowires have ultra-large elastic strain (4-7%), but its elastic strain in composites is limited (less than 1.8%). Recently, we found that the nanowires embedded in the matrix deformed by lattice shear showed ultra-large elastic strain, but the component systems of such nanowire composites are limited. If the particles formed by conventional aging or spheroidizing methods have large elastic strain, it is expected to be widely available. To this end, we have recently explored the elastic deformation behavior of the particles embedded in the matrix deformed by lattice shear. The preliminary findings as follows: the precipitation particles (Ti3Ni4) and spherical particles (Nb) in the NiTi matrix deformed by lattice shear show much larger elastic strain than that in the matrix deformed by dislocation slip, and present the elastic deformation instantaneity, elastic strain distribution non-uniformity, elastic strain relaxation and other characteristics. This project intends to reveal the characteristics, mechanisms and factors of the large elastic deformation instantaneity, elastic strain distribution non-uniformity and elastic strain relaxation of the particles in the matrix deformed by lattice shear, and to clarify the intrinsic link between the elastic deformation of particles and the lattice shear deformation of matrix. It is expected to obtain high-quality academic achievement.

增强相（颗粒、纳米线等）的弹性应变与其复合材料的力学性能密切相关，然而，其在复合材料中的弹性应变较小。例如，单体态纳米线具有超大弹性应变（4-7%），但其在复合材料中的弹性应变却有限（小于1.8%）。最近，我们发现点阵切变基体中纳米线呈现超大弹性应变，但此类纳米线复合材料存在组元体系受限等问题，若采用常规析出或球化方法获得的颗粒具有大弹性应变，则可望获得广泛应用。为此，我们最近探索了点阵切变基体中颗粒的弹性变形行为，初步发现，点阵切变NiTi基体中析出颗粒（Ti3Ni4）与球化颗粒（Nb）呈现的弹性应变均远大于其在位错滑移基体中呈现的弹性应变，且呈现了弹性变形的瞬时性、弹性应变分布非均匀性、弹性应变松弛等特征。本项目拟揭示点阵切变基体中颗粒呈现大弹性变形的瞬时性、弹性应变分布非均匀性、弹性应变松弛等特征、机制及影响因素，阐明其弹性变形与基体切变变形之间的内在联系，可望获得高质量学术成果。

增强相（颗粒、纳米线、纳米带）的弹性应变与其复合材料的力学性能密切相关，然而，其在复合材料中的弹性应变较小，严重限制了其复合材料的力学性能。例如，单体态纳米线具有超大弹性应变（4-7%），但其在复合材料中的弹性应变却很小（小于1.8%）。本项目基于位错滑移型金属基体中的位错与纳米尺度增强相交互作用而导致增强相不能体现超高力学性能的猜测，提出采用形状记忆合金基体的点阵切变变形与纳米尺度增强相的弹性变形相匹配的设计概念，采用常规析出与球化退火的方法制备了Nb颗粒/TiNi记忆合金和Ti2Ni颗粒/TiNi记忆合金两种原位复合材料，利用原位高能X射线衍射实验证实球化颗粒（Nb）与析出颗粒（Ti2Ni）在点阵切变（马氏体相变或去孪晶）型金属基体中均可呈现大弹性应变，弹性应变明显大于在位错滑移基体中所呈现的弹性应变，且其大弹性变形具有快速性、局域性、分布非均匀性、应变松弛等特征，揭示了颗粒增强相在点阵切变机制金属基体中呈现大弹性变形的特征与机制。基于本项目研究，初步建立了点阵切变金属基体中纳米增强相呈现超大弹性应变和超高强度的基本理论，开创了基于应变匹配设计点阵切变金属基复合材料的新领域，为研发高性能金属基材料提供了新理论与新机遇。