7A04铝合金应力腐蚀敏感性及裂纹萌生与扩展行为

采用相移和电化学阻抗谱相结合的方法研究慢应变速率拉伸过程中7A04铝合金在pH=1,4,7,12的3.5%NaCl溶液中应力腐蚀裂纹的萌生和扩展规律,并利用电化学噪声法验证该方法的可行性。结果表明:溶液腐蚀性越强,7A04铝合金的应力腐蚀开裂敏感性越大;pH=1条件下,相移法测得裂纹在1h时开始萌生,在4.5h明显扩展,由电化学阻抗谱分析得到裂纹的萌生和扩展不是连续的,而是分阶段进行;电化学噪声法的测试结果为裂纹在3000~5000s时开始萌生,在13500~22500s扩展明显,伴随出现明显周期性的电流和电位噪声峰。

Susceptibility to Stress Corrosion and Crack Initiation and Propagation of 7A04 Aluminum Alloys

The crack initiation and propagation of 7A04 aluminum alloy in 3. 5％NaCl solution at pH= 1, 4, 7, 12 during slow strain rate test (SSRT) were investigated by the method of combining phase shift with electrochemical impedance spectroscopy. The feasibility of the method was verified by electrochemical noise (EN). The results show that the more corrosive the solution is, the susceptibility of the 7A04 aluminum alloy to stress corrosion cracking is greater; in the solution at pH = 1, the phase shift method shows that crack initiates at 1h and propagates at 4. 5h, and the electrochemical impedance spectroscopy in situ method shows the crack initiation and propagation are discontinuous, and in stages;the EN results show that the crack initiation occurs at a certain moment among 3000-5000s and propagates obviously at a certain moment among 13500-22500s accompanying with obvious periodical current and potential noise peaks.