断续时效对2519A铝合金抗应力腐蚀性能的影响Effect of interrupted aging on stress corrosion resistance of 2519A aluminum alloy

通过双悬臂梁(DCB)应力腐蚀试验、极化曲线测试及透射电镜观察研究断续时效对2519A铝合金抗应力腐蚀性能的影响。结果表明：断续时效T9I6工艺下2519A铝合金的应力腐蚀开裂门槛应力强度因子为29.07 MPa？m^1/2，比T87态铝合金的降低了4.79 MPa？m^1/2。与T87态铝合金相比，T9I6态铝合金极化电阻较小，极化电流较大。合金经T9I6处理后形成大量细小的沉淀相，与T87态铝合金相比，该合金中无沉淀析出带(PFZ)较窄，有利于抗应力腐蚀性能的提高。但T9I6工艺在低温保温阶段于晶界形成的大量细小GP区，再时效后成长为较连续的链状θ′(θ)相，形成腐蚀通道，加速腐蚀的进行。这两方面的竞争作用导致2519A-T9I6铝合金的抗应力腐蚀性能与T87态铝合金的相比略有下降，但其力学性能仍远高于T87态铝合金的。

The influence of interrupted aging on the stress corrosion resistance of 2519A aluminum alloy investigated by double cantilever beam (DCB) test, polarization curve test and transmission electron microscopy(TEM). The results show that the stress corrosion cracking threshold of 2519A-T9I6 aluminum alloy is 29.07 MPa？m^1/2, decreased by 4.79 MPa？m^1/2 when compared to 2519-T87 aluminum alloy. In addition, 2519A-T9I6 aluminum alloy has a smaller polarization resistance and a higher polarization current than 2519-T87 aluminum alloy. On one hand, after T9I6 treatment, 2519A aluminum alloy produces plenty of finer precipitates and narrower precipitate-free zones (PFZs) than 2519-T87 aluminum alloy, which results in the increase of the stress corrosion resistance. On the other hand, the numerous, finer and denser GP zone that created during the process of interrupted aging at a low temperature transforms into continuous θ′(θ) phase, which leads to the increase of the corrosion channel after the re-aging process. So, the velocity of corrosion is accelerated. Because of these two competing reasons, the stress corrosion resistance of 2519A-T9I6 aluminum alloy are just a little lower than that of 2519A-T87 aluminum alloy, while the mechanical properties of 2519A-T9I6 aluminum alloy is much higher than those of 2519A-T87 aluminum alloy.

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