典型服役环境中各向异性高强AZ80镁合金的电偶腐蚀机理与失效机制研究

High-strength AZ80 magnesium alloys coupled with QBe1.7 beryllium bronze fasteners together were equipped to service in aerospace field. In the process of application, galvanic corrosion easily occurred. The corrosion behaviors AZ80 magnesium alloys existed anisotropy due to the textures, resulting the location of crack initiation and growth along the ED (extrusion direction), TD (transverse direction), ND (normal direction) were different. In the preliminary works, we tested “AZ80 magnesium alloy/beryllium bronze” galvanic corrosion weight loss rates along the extrusion direction in the typical service environment. However, the crystallographic anisotropy on the regularity and mechanism of the influence of galvanic corrosion, corrosion crack initiation and propagation mode, failure mechanism and service life needs to be studied further. This project intends to adopt the long cycle of atmospheric exposure tests and electrochemical corrosion, analysis the different orientation of AZ80 alloys galvanic corrosion rates, mechanical strength, crack initiation, propagation mode and mechanisms. The synergistic effect of the crystallographic orientation, service cycles and environments on the corrosion behavior will be expounded. Based on the theory of failure mode and effect analysis, the project will reveal the failure mechanism and corrosion model for different orientation galvanic. Then the service life alloy in service environment will be forecasted reasonably. This project will promote the applications for high-strength AZ80 magnesium alloy in the aerospace and national defense fields.

装备于航空航天的高强AZ80镁合金，通过与铍青铜紧固件偶联，共同构成整体服役。在实际应用过程中，合金极易发生电偶腐蚀。由于变形镁合金织构的存在，其耐腐蚀性能存在各向异性，沿ED(挤压方向)、TD(横向)、ND(法向)腐蚀的萌生点、裂纹扩展方式和耐腐蚀寿命不同。前期预研中，我们测试了典型服役环境中ED方向“AZ80镁合金/铍青铜”的腐蚀失重速率。然而，关于晶体学各向异性对电偶腐蚀的影响规律和作用机理，腐蚀裂纹的萌生及扩展方式，合金断裂失效机制和耐腐蚀寿命等均需进一步研究。本项目拟采用长周期大气暴露试验和电化学腐蚀等手段，分析不同取向的电偶腐蚀速率、力学强度变化规律、腐蚀裂纹萌生与扩展方式及机理；阐述织构、环境因素、服役周期等的协同效应；基于FMEA理论，揭示合金的失效机制，建立腐蚀模型，科学预测合金的服役寿命。通过研究有效推进高强AZ80镁合金在航空航天和国防军工等领域的应用。

本项目工作中，我们取得了一系列重要的研究进展，主要研究内容及实验结果、关键数据主要包括以下几个方面：.(1)采用长周期典型海洋大气暴露试验、电化学腐蚀试验、实验室内的盐雾加速腐蚀试验等手段，分析了各向异性的高强AZ80镁合金在不同取向ED、TD、ND方向上的电偶腐蚀速率、腐蚀深度、腐蚀规律等特征，研究了电偶腐蚀后AZ80镁合金的力学强度衰减变化规律。.(2)典型海洋大气服役环境中，以系统思路为原则，通过灰色关联度分析，进一步阐述了高强AZ80镁合金的微观组织结构、服役环境因素、服役周期等的对其电偶腐蚀产生的协同效应。.(3)基于实验数据，成功研制了新型高强AZ80镁合金大气电偶腐蚀试验装置，发明了一种与真实服役情况相匹配的镁合金电偶腐蚀力学拉伸样品的评价方法，最终揭示AZ80镁合金的失效机制，成功建立了典型海洋服役环境的镁合金腐蚀模型，科学预测合金的服役寿命。.本项目研究的重要科学意义在于：有效避免先进镁合金结构件在服役过程中遭受到过早或意外的损坏，为高强镁合金在海洋大气腐蚀环境中的应用提供必要的理论支持，有效推进高强AZ80镁合金在航空航天和国防军工等领域的应用。