時效對7050鋁合金預拉伸板抗腐蝕性能的影響Effect of aging on corrosion resistance of 7050 aluminum alloy pre-stretching plate

采用硬度、腐蝕速率、剝落腐蝕、慢應變速率拉伸測試及透射電鏡和差示掃描量熱法研究預拉伸后時效制度對7050鋁合金板材顯微組織、硬度和抗腐蝕性能的影響。結(jié)果表明：峰時效合金硬度最大，抗腐蝕性能最差；過時效和回歸再時效與峰時效相比，合金的硬度值減小，抗腐蝕性能變好；在高溫+峰時效中的高溫時效階段，GP區(qū)發(fā)生回溶，有利于η′和η相的直接形核析出，晶內(nèi)析出相長大、不均勻分布，合金硬度減小；晶界析出相粗化、斷續(xù)分布，合金抗腐蝕性能提高。

The effects of aging after pre-stretching process on microstructure, hardness, and corrosion resistance of the 7050 aluminum alloy plate were investigated by means of hardness tests, corrosion rate tests, exfoliation corrosion tests, slow strain rate tensile(SSRT) tests, transmission electron microscopy and differential scanning calorimetry(DSC). The results indicate that the peak-aged 7050 aluminum alloy possesses the highest hardness, but its corrosion resistance is poor. The overaging and the retrogression and re-aging treatments lower the hardness, but improve the corrosion resistance of the 7050 aluminum alloy compared with the peak-aging treatment. At the high temperature aging stage of the high temperature and a subsequent low temperature aging, GP zone can be reversed, which is beneficial to the nucleation of η′ and η phases. Consequently, the precipitates within grains become coarser and distribute uniformly, leading to the decrease of hardness. Meanwhile, the precipitates at grain boundaries become coarser and discontinuous resulting in an improved corrosion resistance.

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