新型高强度BCC结构Mg-11Li-xAl/Zn合金的腐蚀损伤机制及表面膜研究

镁锂合金是最轻的结构用金属材料，然而低的绝对强度和差的耐蚀性一直是制约其发展与应用的瓶颈问题。本项目针对新型可固溶热处理强化的BCC结构Mg-11Li-xAl/Zn合金，系统研究其静态腐蚀与应力腐蚀行为、失效机制及表面膜。首先，通过腐蚀形貌的微观表征、原位观察和局部腐蚀电流分布的动态检测，揭示合金静态腐蚀萌生与扩展机制，阐明Al/Zn合金元素、固溶热处理和第二相等对腐蚀损伤的影响规律；然后，通过表面膜的形貌、结构、成分、损伤再钝化行为、电化学-光谱学信息等研究，分析表面膜动态生长机理及其物理化学特性；最后，利用力学-电化学-微观观察耦合技术研究材料的应力腐蚀行为，探明材料力学-腐蚀-微观组织的内在协同作用关系。本项目的实施不仅深入表征了高强BCC结构Mg-Li-Al/Zn合金的腐蚀行为及其表面膜特性，也为高强高耐蚀Mg-Li合金的设计与应用提供了新的思路和技术支撑。

Mg-Li alloy is the lightest weight and ideal structural-metallic-material, whereas the low absolute mechanical strength and poor corrosion resistance are always the bottleneck problems for its development and application. Based on the body-centered cubic (BCC) structured Mg-Li-Al/Zn alloys strengthened by solution treatment, this project will be carried out to confirm the optimal composition of Al/Zn and the solution treatment process, meanwhile the static corrosion, stress corrosion and surface films of the proposed alloys are studied in detail. Firstly, the mechanisms of corrosion initiation, propagation and failure will be revealed by investigating the corrosion morphologies and monitoring the distribution of local corrosion current. And then, the effect of Al/Zn element, solution treatment and second phases on the corrosion behaviors is further illuminated systemically. Secondly, the growth mechanism and stability of corrosion surface film will be analyzed by investigating the morphologies, structure, composition, repassivation after scratching and coupled electrochemistry-spectral information. Thirdly, stress corrosion behaviour will be elucidated by the coupled mechanical-electrochemical-microstructural technology, containment with revealing the coordinated relation of mechanical property, electrochemical property and microstructure evolution. Thus, the current project will not only elucidate the corrosion behaviors and surface film of high-strength BCC Mg-11Li-xAl/Zn alloys, but also provide the novel method and technological support for the optimized design and application of high-strength and high-corrosion-resistant BCC Mg-Li alloys in the near future.