ABSTRACT

In this study, the effects of pre-deformation on mechanical properties and stress corrosion cracking behaviour of 7075 alloy was investigated with SSRT and electrochemical polarization. The 10% pre-deformation substantially improves the SCC resistance of the 7075 alloys. The strain induced dislocations act as diffusion shortcuts and result in enhanced precipitation and early appearance of GBPs in the naturally aged 7075-T3. For artificial aging, pre-deformation causes rapid over-aging as larger precipitates are found in both matrix and GBs of the 7075-T8. The substitution of Cu for Zn in the GBPs and the larger GBPs acting as hydrogen traps are possible explanations for the improved SCC resistance of 7075-T8. Further improvements in SCC resistance can be found in the RRA treated 7075 alloys, while a more ductile behaviour can be seen in the pre-deformed 7075 alloy. Additionally, results of electrochemical testing are in high correlation with the SSRT results.

摘要

本研究采用SSRT和电化学极化研究了预变形对7075合金力学性能和应力腐蚀开裂行为的影响。10% 的预变形显着提高了 7075 合金的 SCC 抗性。应变诱导位错充当扩散捷径，导致自然时效 7075-T3 中 GBP 的析出增强和早期出现。对于人工时效，预变形会导致快速过时效，因为在 7075-T8 的基体和 GB 中都发现了较大的沉淀物。GBPs 中 Cu 替代 Zn 和较大的 GBPs 充当氢陷阱是 7075-T8 改善的 SCC 抗性的可能解释。在 RRA 处理的 7075 合金中可以发现抗 SCC 性能的进一步改进，而在预变形的 7075 合金中可以看到更具延展性的行为。此外，电化学测试的结果与 SSRT 结果高度相关。