时效对7050铝合金预拉伸板抗腐蚀性能的影响

摘要

采用硬度、腐蚀速率、剥落腐蚀、慢应变速率拉伸测试及透射电镜和差示扫描量热法研究预拉伸后时效制度对7050铝合金板材显微组织、硬度和抗腐蚀性能的影响。结果表明：峰时效合金硬度最大，抗腐蚀性能最差；过时效和回归再时效与峰时效相比，合金的硬度值减小，抗腐蚀性能变好；在高温+峰时效中的高温时效阶段，GP区发生回溶，有利于η′和η相的直接形核析出，晶内析出相长大、不均匀分布，合金硬度减小；晶界析出相粗化、断续分布，合金抗腐蚀性能提高。%The effects of aging after pre­stretching 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 peak­aged 7050 aluminum alloy possesses the highest hardness, but its corrosion resistance is poor. The overaging and the retrogression and re­aging treatments lower the hardness, but improve the corrosion resistance of the 7050 aluminum alloy compared with the peak­aging 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.