时效析出相微结构改变对AA2024铝合金应力腐蚀行为的影响

The influence of precipitation microstructure change on the stress corrosion behavior of AA2024 aluminum alloy

摘要:

通过恒载荷应力腐蚀实验、扫描电镜（SEM）和透射电镜（TEM）等测试方法，研究了时效处理中析出行为的变化对AA2024铝合金应力腐蚀行为的影响。结果表明，合金在T3态时对应力腐蚀较为敏感，进行T8时效处理后，合金的应力腐蚀敏感性显著降低。利用高角环形暗场成像扫描透射电镜技术（HAADF-STEM）对合金进行准原位腐蚀实验观察，研究了合金T3和T8时效状态下的腐蚀过程和析出行为的变化情况，直观地展示了不同时效状态合金的腐蚀形态：T3态的合金为晶间腐蚀形貌，T8态的合金为晶间腐蚀和晶粒腐蚀相结合。由于析出行为和腐蚀机制的改变，不同时效状态的AA2024铝合金的应力腐蚀敏感性不同。

Abstract:

The effect of precipitation microstructure change on the stress corrosion behavior of AA2024 aluminum alloy was investigated by constant load stress corrosion tests, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the T3 alloy is much more sensitive to stress corrosion than the T8 alloy. The corrosion process and precipitation microstructure change of T3 and T8 alloys were investigated by in-situ corrosion observations operated by high-angle annular dark-field scanning TEM (HAADF-STEM), which intuitively demonstrate the different corrosion morphologies: the corrosion morphology of T3 alloy is intergranular corrosion and that of T8 alloy is a combination of intergranular corrosion and grain attack. Because of the change in precipitation microstructure and corrosion mechanism, the alloys with different ageing conditions possess different stress corrosion susceptibility.