斷續(xù)時效對2519A鋁合金抗應(yīng)力腐蝕性能的影響Effect of interrupted aging on stress corrosion resistance of 2519A aluminum alloy

通過雙懸臂梁(DCB)應(yīng)力腐蝕試驗、極化曲線測試及透射電鏡觀察研究斷續(xù)時效對2519A鋁合金抗應(yīng)力腐蝕性能的影響。結(jié)果表明：斷續(xù)時效T9I6工藝下2519A鋁合金的應(yīng)力腐蝕開裂門檻應(yīng)力強度因子為29.07 MPa？m^1/2，比T87態(tài)鋁合金的降低了4.79 MPa？m^1/2。與T87態(tài)鋁合金相比，T9I6態(tài)鋁合金極化電阻較小，極化電流較大。合金經(jīng)T9I6處理后形成大量細(xì)小的沉淀相，與T87態(tài)鋁合金相比，該合金中無沉淀析出帶(PFZ)較窄，有利于抗應(yīng)力腐蝕性能的提高。但T9I6工藝在低溫保溫階段于晶界形成的大量細(xì)小GP區(qū)，再時效后成長為較連續(xù)的鏈狀θ′(θ)相，形成腐蝕通道，加速腐蝕的進(jìn)行。這兩方面的競爭作用導(dǎo)致2519A-T9I6鋁合金的抗應(yīng)力腐蝕性能與T87態(tài)鋁合金的相比略有下降，但其力學(xué)性能仍遠(yuǎn)高于T87態(tài)鋁合金的。

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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