采用硬度测试、电导率测试、透射电镜、电化学等手段研究双级时效对7050铝合金板材力学性能和剥落腐蚀性能的影响.研究结果表明:经低温短时时效后,晶内析出相主要为GP区和矿相,高温二级时效的引入使晶内析出相逐渐转变为η相;随着二级时效时间的延长,晶内η相和晶界平衡相逐渐粗化,晶界无沉淀析出带(PFZ)变宽,合金的硬度先升高后降低,连续分布的腐蚀通道转变为断续的腐蚀点,板材抗剥落腐蚀性能提高；剥蚀起源于点蚀的萌生和发展,但剥蚀的发展依赖于合金晶界的形貌和化学组成,随着时效时间的延长,剥蚀程度先增大后减小再变大.%The influence of the two-step aging time on the mechanical properties and exfoliation corrosion susceptibility of a 7050 aluminum alloy plate was investigated by means of hardness tests, conductivity tests, transmission electron microscopy(TEM), electrochemical impedance spectroscopy(EIS). The results show that through the aging at low temperature for a short time, the main age-hardening precipitates in the matrix are GP zone and n' phase, then through the second step aging at elevated temperature the age-hardening precipitates are transformed to n phase gradually. And with the increase of the aging time, the r phase and precipitates on grain boundary become coarser gradually, PFZ becomes wider at the same time, which results in the increase of hardness, then decreases and continuous channels become discontinuously distributed, and the resistance to exfoliation corrosion of the 7050 aluminium alloy plate is improved. The exfoliation corrosion development depends on grain boundary microstructure and chemical composition, starts and expands with formation and development of pitting corrosion. With the increase of the aging time, the exfoliation corrosion degree becomes serious, then improves, and serious again.
展开▼
