预拉伸对7050铝合金腐蚀性能的影响

Effects of pre-stretching on corrosion resistance of 7050 aluminum alloy

通过硬度、电导率、Tafel极化曲线、慢应变速率拉伸测试及光学显微镜、透射电镜组织观察,研究预拉伸变形量对7050铝合金板材强度和腐蚀性能的影响。研究结果表明:预拉伸引入大量位错,在时效过程中促进η平衡相的形核;随着预拉伸变形量的增大,晶内η相增多、粗化,合金的强度降低,电导率升高;随着预拉伸变形量增大,合金内的位错密度增大,空位浓度降低,晶界析出相间距先增大后减小,抗腐蚀性能先增大后减小;无沉淀析出带(PFZ)先变宽后消失,抗腐蚀性能先减小后增大;综合晶界析出相的分布和PFZ宽度的共同影响,随着预拉伸变形量的增大,板材的抗腐蚀性能先逐渐减小后迅速降低。

The effects of pre-stretching on strength, corrosion resistance and microstructure of 7050 aluminum alloy plate were studied by hardness, electrical conductivity, Tafel curves, slow strain rate tensile（SSRT）, optical microscopy and transmission electron microscopy tests. The results show that many dislocations are generated in the process of pre-stretching, and the dislocations can provide efficient nucleation sites for η phase during the aging. With the increase of the pre-stretching deformation, the number and size of the η phase within grains increases, which results in the reduction in the mechanical strength and improvement in the electrical conductivity. As the density of dislocations increases, the vacancy concentration decreases, which makes the distance between precipitates at grain boundaries become relatively lager first, and then reduce, and the corrosion resistance improve first, and then decrease. Meanwhile, precipitate-free zones （PFZ） become wider first, and then gradually disappear with the increase of the pre-stretching deformation, which causes the corrosion resistance to decrease first, and then improve. So, under the influence of the precipitates at grain boundaries and the PFZ together, the corrosion resistance gradually decreases first, and then decreases quickly with the increase of the pre-stretching deformation.