Research on fatigue damage of aluminum/steel dissimilar joints is critical to ensure the reliability of multi-material lightweight structures. In this study, the fatigue crack propagation (FCP) characteristics of the interface, weld, and heat-affected zone (HAZ) of aluminum/steel laser-metal inert gas (MIG) fusion-brazed joints were investigated. Additionally, the influencing role of the microstructure of different micro-zones on the FCP behaviors was discussed. Single-edge notched tensile (SENT) specimens of the interface region exhibited a higher crack growth rate and crack threshold than SENT-weld and SENT- HAZ specimens due to the highly hard and brittle nature of the intermetallic compounds (IMC) at the aluminum/steel interface. Moreover, the fatigue fracture surface of SENT-interface specimens showed a brittle fracture pattern without fatigue striation characteristics, which was different from aluminum/steel solid-state and traditional aluminum alloy welded joints. Electron backscatter diffraction (EBSD) analysis results revealed that the synergistic effects of grain size, sub-grain boundaries, and micro-performance all contributed to the crack deflection of SENT-weld at a large angle to the HAZ, thereby resulting in more optimized crack resistance in the weld zone.

中文翻译：

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铝/钢激光金属惰性气体熔钎焊接头不同微区疲劳裂纹扩展特性

铝/钢异种接头的疲劳损伤研究对于确保多材料轻量化结构的可靠性至关重要。在这项研究中，研究了铝/钢激光金属惰性气体（MIG）熔焊接头的界面、焊缝和热影响区（HAZ）的疲劳裂纹扩展（FCP）特性。此外，还讨论了不同微区的微观结构对FCP行为的影响。由于铝/金属间化合物 (IMC) 的高硬和脆性，界面区域的单边缺口拉伸 (SENT) 样品比 SENT 焊接和 SENT-HAZ 样品表现出更高的裂纹扩展速率和裂纹阈值。钢接口。此外，SENT界面试样的疲劳断口呈现脆性断裂模式，不具有疲劳条纹特征，这与铝/钢固态和传统铝合金焊接接头不同。电子背散射衍射（EBSD）分析结果表明，晶粒尺寸、亚晶界和微观性能的协同效应均导致SENT焊缝的裂纹偏转与热影响区大角度，从而产生更优化的裂纹焊接区的电阻。