时效对7050铝合金预拉伸板抗腐蚀性能的影响
第23卷第3期中国有色金属学报 2013年3月 V ol.23 No.3 The Chinese Journal of Nonferrous Metals Mar. 2013 文章编号：1004-0609(2013)03-0645-07
时效对 7050铝合金预拉伸板抗腐蚀性能的影响
宋丰轩，张新明，刘胜胆，韩念梅，花 隆
(中南大学 材料科学与工程学院，长沙 410083)
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。
关键词：7050铝合金；预拉伸；时效；腐蚀性能
中图分类号：TG 146.2 文献标志码：A
Effect of aging on corrosion resistance of
7050 aluminum alloy pre-stretching plate
SONG Feng-xuan, ZHANG Xin-ming, LIU Sheng-dan, HAN Nian-mei, HUA Long
(School of Materials Science and Engineering, Central South University, Changsha 410083, China)
Abstract: 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.
Key words:7050 aluminum alloy? pre-stretching? aging? corrosion resistance
7050铝合金预拉伸厚板由于综合性能较好，已大 量用作飞机的机身框架、翼梁、尾翼等部件 [1] 。预拉 伸厚板的生产是在固溶淬火后、时效前引入一定量的 预拉伸变形，来消除淬火过程中产生的残余应力，以 避免应力释放引起的构件变形甚至报废 [2] 。但拉伸变 形在合金内引入大量位错， 有利于η相(MgZn2)的形核 析出，η 相的析出长大使得主要强化相 η′相的析出减 少，合金强度降低；同时晶界析出相变小且呈连续分 布，抗腐蚀性能降低 [3?4] 。
时效是铝合金预拉伸厚板生产的最后一步，通过 不同的时效热处理可以精确调控析出相在合金晶内和 晶界的分布，以得到综合性能优良的产品。目前，应 用最广泛的时效热处理制度包括：一级峰时效(T6)， 二级过时效(T7x)和三级回归再时效(RRA)。峰值时效
基金项目：国家重点基础研究发展计划资助项目(2012CB619502)
收稿日期：2012-04-28；修订日期：2012-11-27
通信作者：张新明，教授，博士；电话：0731-88830265；E-mail：xmzhang@https://www.wendangku.net/doc/ad1834316.html,