铝合金中空位-溶质复合体的演化及其对强化相析出的调控机理

缺乏直接观测导致人们对铝合金时效过程空位及其与溶质原子复合行为的认识非常有限，析出相形核、转变和调控的原子尺度机制这一科学难题一直未解决。本项目融合实验和理论，研究空位-溶质原子复合行为及其对析出相演变的作用。采用同步辐射X射线吸收精细结构谱并关联正电子湮灭谱、低辐照损伤球差校正电镜和三维原子探针等先进表征技术，测定典型铝合金强化相形核和转变过程局部原子结构变化，建立亚稳相、人工时效早期团簇和自然时效团簇中的空位-溶质复合体构型。结合局部精细结构解析、原位观察和能量计算，在原子尺度揭示自然/人工时效过程空位-溶质复合的动态模型，阐明空位对铝合金析出相形核和转变的作用机制。通过表征微量元素、预变形和预时效对空位-溶质复合体构型的改变，理清调控析出的精准机理。总结上述研究建立空位原子尺度调节时效析出的新理论，发展基于调控空位的铝合金成分和制备工艺设计准则，为开发高性能铝合金提供原创理论支撑。

The lack of direct observation leads to a limited understanding of the vacancy and its complexing behavior with solute atoms in the aging process of aluminum alloy. The core scientific problem of the atomic scale mechanism of nucleation, transformation and regulation of precipitates has not been solved. In this project, experiments and theories are integrated to study the complex behavior of vacancy/solute atoms and its effect on the evolution of precipitates. By using Synchrotron radiation X-ray absorption fine structure spectrum, Positron annihilation spectrum, low-irradiation-damage spherical aberration-corrected Electron Microscopy and three-dimensional Atom Probe, the local atomic structure changes in the process of strengthening phase nucleation and transformation of typical aluminum alloy will be measured, and the structure of vacancy-solute complex in metastable phase, clusters in early-stage artificial aging and clusters in natural aging will be also established. Combined with local fine structure analysis, in-situ observation and energy calculation, the dynamic model of vacancy-solute complex in natural/artificial aging process is revealed at the atomic scale, and the mechanism of vacancy effect on the nucleation and transformation of precipitated phase in aluminum alloy is clarified. By characterizing the structural change of the vacancy-solute complex caused by micro-alloying, pre-deformation and pre-aging, the precise mechanism of tuning precipitation will be unraveled. Based on the above research, a new theory of adjusting aging precipitation by vacancy at atomic scale will be established. This project will develop new design criteria based on adjusting vacancy for the aluminum alloy composition and preparation process, providing original theoretical support for the development of high-performance aluminum alloys.