预拉伸变形对Al-Cu-Mg合金腐蚀性能的影响

摘要

采用表面腐蚀、慢应变速率拉伸(SSRT)实验研究预拉伸变形对Al-Cu-Mg合金腐蚀性能的影响。利用扫描电镜观察分析Al-Cu-Mg合金断口形貌及结构。结果表明，预拉伸变形可显著提高合金位错密度，为H原子的扩散提供更多的通道，因此，在相同腐蚀时间下，3.5%NaCl溶液中T8态Al-Cu-Mg合金的腐蚀速率高于T6态。此外，预拉伸变形可显著增加S相弥散度，使得S相两侧的无沉淀析出带变窄，有效降低了晶界和晶内的电位差，从而降低晶界沉淀相的溶解速度，因此，在同一热处理状态下，Al-Cu-Mg合金在饱和H2S溶液中的应力腐蚀开裂敏感性高于干燥空气中的腐蚀开裂敏感性。同一应变速率下，T8态Al-Cu-Mg合金具有比T6态更好的抗应力腐蚀性能，表明预拉伸变形处理可显著提高合金的抗应力腐蚀性能。%The corrosion behavior of Al-Cu-Mg alloy was investigated by a combination of the surface corrosion and slow strain rate tension (SSRT). The fracture surface of each investigated condition was characterized by scanning electron microscopy (SEM). The results show that, by pre-stretching, the dislocation density can be improved with providing more channels for the diffusion of H atoms, the corrosion rate of the Al-Cu-Mg alloy in T8 temper is higher than that of T6 temper in 3.5%NaCl solution for the same period. The dispersity of S phase was dramatically increased by pre-stretching with the no-precipitation band narrows on both sides of S phase, reducing the potential difference between the grain boundary and grain interior. Al-Cu-Mg alloy is more susceptible to Stress Corrosion Crack (SCC) in saturated H2S solution than in dry air. Compared to T6 treatment, pre-stretching is beneficial to enhance the SCC resistance of Al-Cu-Mg alloy at the same strain rate.