Wen Weiling, Carlson Blair, Banu Mihaela
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
General Motors Research & Development, Warren, MI 48090, USA.
Materials (Basel). 2024 Jul 17;17(14):3542. doi: 10.3390/ma17143542.
Aluminum-steel joints are increasingly used in the automotive industry to meet the requirements for energy saving and emission reduction. Among various joining technologies, self-pierce riveting (SPR) and resistance spot welding (RSW) are two well-established technologies for fabricating dissimilar joints with stable and high mechanical performance. However, corrosion will occur in these joints inevitably due to different electrochemical properties, which can degrade the surface quality and the mechanical performance, such as strength. This paper presents a method of understanding the corrosion mechanisms in joining aluminum and steel. For this understanding, a hybrid method combining experimental observations, mechanical properties identification, and analytical approaches was used to assess the evolution of the impact of corrosion on the joining performance, such as traction separation curves. The study was conducted on common combinations used in the vehicles, e.g., a 1.2 mm thickness aluminum alloy (AA 6022) and 2.0 mm thickness hot deep galvanized steel (HDG HSLA 340) joined by SPR and RSW. After the fabrication of these joints, accelerated cyclic corrosion tests of up to 104 cycles were performed, which reproduced the environmental conditions to which a vehicle was exposed. By investigating the microstructural evolution within the joints, the corrosion mechanisms of SPR and RSW joints were revealed, including the initiation and propagation. Moreover, the intrinsic impact of the corrosion on the mechanical performance, including the strength, axial stiffness, and crashworthiness, was analyzed by performing a lap-shear test. It showed that as corrosion proceeds, the fracture modes and mechanical performance are affected significantly.
铝钢接头在汽车工业中越来越多地被使用，以满足节能减排的要求。在各种连接技术中，自冲铆接（SPR）和电阻点焊（RSW）是两种成熟的技术，用于制造具有稳定和高机械性能的异种接头。然而，由于不同的电化学性质，这些接头不可避免地会发生腐蚀，这会降低表面质量和机械性能，如强度。本文提出了一种理解铝钢连接中腐蚀机制的方法。为了实现这一理解，采用了一种结合实验观察、力学性能识别和分析方法的混合方法，来评估腐蚀对接头性能（如拉伸分离曲线）的影响演变。该研究针对车辆中常用的组合进行，例如，通过SPR和RSW连接的1.2毫米厚铝合金（AA 6022）和2.0毫米厚热镀锌高强度低合金钢（HDG HSLA 340）。在制造这些接头后，进行了高达104次循环的加速循环腐蚀试验，该试验再现了车辆暴露的环境条件。通过研究接头内部的微观结构演变，揭示了SPR和RSW接头的腐蚀机制，包括腐蚀的起始和扩展。此外，通过进行搭接剪切试验，分析了腐蚀对力学性能（包括强度、轴向刚度和耐撞性）的内在影响。结果表明，随着腐蚀的进行，断裂模式和力学性能受到显著影响。
