基于纳米“团簇-有序相”调控BCC镁锂合金强度及热稳定性机理研究

镁锂合金作为最轻的金属结构材料具有广阔的轻量化应用前景，但强度和热稳定性不足是限制其发展的瓶颈。申请人近期研究发现，合金元素铝协同银诱导BCC镁锂合金中纳米“团簇-有序相”析出显著提升了合金的强度及热稳定性，然而其形成、演化及其对力学性能的影响规律与微观机理尚不明确。本项目拟以铝与银协同合金化的BCC镁锂合金为研究对象，利用原位同步辐射高能X射线衍射、球差校正透射电镜及三维原子探针展开以下研究：探究铝-银协同合金化诱导纳米团簇和有序相的形成及演化规律，建立组织演化模型；阐明纳米“团簇-有序相”对强度及热稳定性的影响规律，构建纳米组织与力学性能的关系模型；解析“团簇-有序相”及其界面的微纳结构及成分特征，探究“团簇-有序相”与位错的交互作用行为，深入揭示纳米“团簇-有序相”调控BCC镁锂合金强度及热稳定性的机理。本项目的实施将为超轻高强高热稳定性镁锂合金研发奠定理论基础。

Magnesium-lithium alloys are lightest metallic structural materials and, as such, offer significant potential use as engineering materials. However, low strength and thermal stability limit their wider application. The applicant recently found that strength and thermal stability can be dramatically enhanced by nano-sized clusters and ordered precipitates that are induced by synergistic alloying of aluminum and silver in BCC magnesium-lithium alloys. But the formation and evolution mechanisms of nano-sized clusters and ordered precipitates, and their effects on mechanical properties are still unknown hitherto. The project aims at studying the microstructure and mechanical properties of BCC magnesium-lithium alloys with synergistic alloying of aluminum and silver by in-situ Synchrotron high-energy X-ray diffraction, spherical-aberration-corrected Transmission Electron Microscopy and three-dimensional Atom Probe Tomography. The formation and evolution of nano-sized clusters and ordered precipitates induced by synergistic alloying of aluminum and silver will be investigated and the structural evolution model will be established. The effects of nano-sized clusters and ordered precipitates on strength and thermal stability will be clarified, and the relationship model between microstructure and mechanical properties will be established. The multiscale structural characteristics and quantitative compositional analysis of "clusters-ordered precipitates" and their interfaces will be analyzed, and the interaction behavior between "clusters-ordered precipitates" and dislocations will be explored. This project will reveal the microscopic mechanism of nano-sized "clusters-ordered precipitates" on tuning strength and thermal-stability in BCC magnesium-lithium alloys and, thereby, lay theoretical foundations for designing of ultralight, high-strength and thermally stable magnesium-lithium alloys.