用直读光谱仪、万能材料试验机、光学显微镜、扫描电子显微镜等分析手段，分析高速列车7020铝合金车钩梁多处开裂现象及其原因。结果表明，开裂的7020铝合金车钩梁材料质量正常，服役后的车钩梁基体表面存在腐蚀坑，腐蚀坑中存在Cl-离子，主裂纹位于焊接热影响区和母材交界处，裂纹沿晶扩展。实验室采用和车钩梁相似的环境和受力状况进行模拟试验，高强度合金双悬臂梁试样的应力腐蚀开裂（SCC）裂纹形貌特征和车钩梁裂纹吻合良好，表明车钩梁开裂原因为SCC，并讨论了铝合金的SCC机理。
By means of optical emission spectrometer, universal material testing machine, optical microscope, scanning electronic microscope and finite element calculation were used to analyze the multi-cracking reason of 7020 aluminum alloy train coupler girder, and study results indicated that stress corrosion cracking (SCC) caused by wet and sweltering hot weather .According to finite element calculation results it could be known there was no stress at the “Z” direction, and welding residual tension stress is the main cracking reason. Modeling test results of DCB samples showed that the cracking mode of train coupler girder and DCB sample is same. Cracking mechanism of 7020 aluminum alloy was researched and discussed.
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