高强铝合金冷喷涂层搅拌摩擦焊接接头腐蚀机理与寿命预测研究

Corrosion performance of high strength aluminum aircraft structures is a high concern in whole world aerospace industries. The corrosion resistance optimisation and protection, the corrosion liability of friction stir welded aluminum alloys in long term service are both the important problems，which forbidden the advanced application of friction stir welding in aerospace manufactures. Cold sprayed coatings are applied in friction stir welds to improve the corrosion performance. The corrosion behavior and evolution mechanism are primarily considered, including the different zones of the welds with and without coatings under different coating conditions. The formation mechanism and factors on corrosion behavior are discussed. The mechanism of cold spray on corrosion performance is deeply studied. The mathematic model of corrosion life prediction is established based on the understanding of corrosion mechanism and corrosion evolution mechanism. The corrosion life is simulated and assessed using finite element numerical simulation. This research could provide a new corrosion life assessment method. The research has important scientific significance and high economic in industry application, especially for long term service structure.

大型飞行器结构的腐蚀是世界航空界共同面临的重大问题，搅拌摩擦焊在我国航空领域的推广和应用，其中必须解决的关键问题之一就是铝合金焊缝区的腐蚀与防护，以及长期服役过程中抗腐蚀性能可靠性问题。本项目通过冷喷涂层技术实现焊接接头腐蚀性能优化，研究冷喷涂层处理前后接头微区、涂层不同状态下的腐蚀行为及演变规律；掌握高强铝合金搅拌摩擦焊接头腐蚀行为的形成原因及影响因素；揭示冷喷涂层与接头腐蚀机理和腐蚀动力学规律；探索冷喷涂层技术提高焊接接头腐蚀性能的机理；建立腐蚀寿命预测的精准数学模型。采用有限元数值模拟方法实现焊接接头腐蚀寿命预测与可靠性评估，为长期服役环境下焊接结构的腐蚀寿命预测提供理论基础以及新的计算与评价方法。项目的研究内容不仅具有重要的科学意义，同时也为FSW技术工程实际应用、长期服役条件下腐蚀寿命预测与评估奠定重要的技术支撑和理论依据。

成功制备冷喷涂层并通过ABAQUS对冷喷涂过程进行数值模拟，结果表明喷涂过程中最高温度已经基本达到了材料熔点。结合数值模拟、DSC-TGA及SEM试验结果，冷喷涂层的结合机理主要是由金属射流相互连接形成的机械结合为主；但结合界面附近存在少量的熔化现象，即局部区域存在冶金结合。.在不同腐蚀介质（剥落腐蚀、晶间腐蚀）中，冷喷涂层均表现出了非常好的耐腐蚀性能，其耐腐蚀性远优于母材区及FSW接头热影响区，与焊核区相当。冷喷涂层使得焊缝区域的组织和第二相粒子的分布趋于均匀，有效了焊缝区域的耐蚀性。.基于Comsol多物理场仿真软件，建立有限元模型对2219铝合金搅拌摩擦焊接头及冷喷涂层保护的搅拌摩擦焊接头的腐蚀行为进行数值模拟，结果显示，有限元模型的接头的腐蚀深度与冷喷涂层的腐蚀深度结果与试验数据具有较好的一致性，证明了冷喷涂层能提高接头的抗腐蚀能力。