α-Al纳米晶复合非晶Al合金微结构特性对耐点蚀作用机理研究

The α-Al nanocrystals precipitated amorphous Al alloys have broad prospect of applications in aerospace field due to their high specific strength and excellent corrosion resistance. It is found that the existence of nano α-Al particles increases the pitting corrosion resistance of this kind of composites, which is closely related to the sizes of the α-Al particle and the composition profiles in the amorphous matrix. To date, the influence of the microstructure characteristics on the pitting corrosion in this kinds of α-Al nanocrystals precipitated amorphous Al alloys remains unclear and is urgent to be clarified. In this project, the Al-TM (transition metal elements)-RE (rear earth elements) alloy systems are selected. The binary Al-TM and Al-TE alloy are firstly selected to systematically study the effecs of the size of the α-Al nanocrystals, composition profiles in the amorphous matrix upon the corrosion resistance. The detailed contents contain three aspects: (1) atomic-scale and quantitative measurements and analyses of the composition profiles in the amorphous matrix around nanoscale α-Al phase. (2) the feature of the TM and RE independently and synergistically affecting the corrosion resistance of α-Al/amorphous composites. (3) The size effect of α-Al nanophases in altering the compositional distribution in the remaining amorphous matrix and the corrosion resistance of amorphous composites. (4) Based on the obtained relationship between the microstructure characteristics and the pitting corrosion, the high corrosion resistant amorphous Al alloys could be designed. This will provide scientific evidences and application foundation for enhancing the practical applications of Al-based amorphous composites in many important industrial fields.

α-Al纳米晶复合非晶Al合金因其高比强度、高耐蚀性在航空航天领域有着广阔的应用背景。研究发现，α-Al纳米晶的存在可显著提高该类材料的耐点蚀能力，而这与α-Al晶体尺寸、相界面组元分布等特性有关。迄今，该类复合材料中微结构特性与微观点蚀行为的内在关联性尚不清楚，亟待澄清。本项目拟以Al-TM（过渡族元素）-RE（稀土元素）体系为研究对象，从Al-RE及Al-TM二元合金出发，系统地研究α-Al相尺寸、非晶基体的界面成分分布与腐蚀性能的内在联系。主要内容包括：1）α-Al相周围非晶基体成分的原子尺度定量表征；2）TM及RE元素影响腐蚀性能的本质及二者的协同作用机制；3）α-Al纳米粒子尺寸对界面成分分布特性及腐蚀性能的影响规律；4）以非晶Al合金复合材料微区成分对腐蚀性能的作用机理研究成果指导下，进行高耐蚀新型非晶Al合金成分设计，为推动其作为高耐蚀防护涂层的应用提供重要的科学与应用依据。

非晶态 Al 合金是最具应用前景的涂层材料之一，成分和结构的均匀特性，使其具有较高的耐局部腐蚀能力；组元固溶度的扩展，则可大幅提高活性缓蚀元素的浓度。因此，国内外学者长期致力于研究非晶 Al 合金涂层制备、组元特性与腐蚀关联性，以及活性缓蚀离子按需释放机理等方面。但是关于TM（过渡族元素）和RE（稀土元素）对钝化膜稳定性的影响缺乏深入的理解，TM和RE对钝化膜稳定性的协同作用也未澄清，适用于铝基非晶合金缓蚀离子的设计也鲜有报道，这些因素限制了高耐蚀铝基非晶合金的设计、制备与应用。因此，本项目以Al-TM-RE体系为研究对象，从Al-RE及Al-TM二元合金出发，系统地研究了非晶基体的界面成分分布、腐蚀产物、缓蚀离子等与腐蚀性能的内在联系，主要研究成果总结如下：（1）以Al-Y二元非晶为研究体系，克服晶体材料中结构和成分不均匀性对腐蚀性能的影响并排除了其他耐蚀性元素的干扰，发现Al-Y非晶合金的钝化膜阻抗随Y含量升高而提高，半导体特性表现为p型，钝化稳定性的提高归因于Y元素掺杂形成YAlO3复合氧化物，揭示了Y元素对于铝基非晶腐蚀的本征作用。（2）澄清了Ce在Al-Co-Ce非晶合金腐蚀过程中所扮演的角色，优化筛选出了最优的Ce含量。发现Ce含量为4 at.%时，Al-Co-Ce非晶合金具有最低的钝化电流密度（ipass）和钝化膜载流子密度（ND），表明具有最好的耐蚀性，为铝基非晶合金的成分优化设计提供重要的指导。（3）针对铝基（Al-TM-RE）非晶合金，利用阻抗谱检测技术和等效电路图模型分析了其长期腐蚀机制。结合FIB/TEM技术分析了钝化膜在长期条件下的演化规律，阐明了TM和RE元素对铝基非晶钝化膜稳定性的协同作用机制。（4）利用Al基非晶合金结构和化学均匀性的特点，排除传统晶态Al合金结构缺陷带来的干扰，澄清了硝酸盐对Al基非晶合金的缓蚀机理并发现了缓蚀临界浓度，对于有效利用硝酸根离子提升Al非晶合金腐蚀性能提供了重要依据。