(1. 中南大学 材料科学与工程学院，长沙410083；
2. 中南大学 有色金属材料科学与工程教育部重点实验室，长沙410083；
3. 中南大学 轻质高强结构材料国防科技重点实验室，长沙 410083；
4. 中南大学 有色金属先进结构材料与制造协同创新中心，长沙 410083)
摘 要: 采用慢应变速率拉伸(SSRT)试验、金相显微镜(OM)、扫描电镜(SEM)和透射电镜(TEM)等手段研究了微量元素Ge对7020铝合金板材应力腐蚀断裂敏感性的影响。通过比较不含Ge和含Ge板材中晶内η′强化相尺寸与体积分数的差异分析了合金强度下降的原因；通过比较不含Ge和含Ge板材中晶粒组织和晶界η相的尺寸、间距及化学成分的差异分析了合金应力腐蚀断裂敏感性下降的原因。结果表明：加入Ge元素后，板材SSRT的抗拉强度更低，在NaCl溶液中的强度和伸长率较空气中的下降率也更低，应力腐蚀指数由0.059减小至0.017，应力腐蚀断裂敏感性明显降低。
关键字: 7020铝合金；Ge；应力腐蚀断裂；显微组织
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China;
3. The National Key Laboratory of Science and Technology for National Defence on High-strength Lightweight Structural Materials, Central South University, Changsha 410083, China;
4. Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center, Central South University, Changsha 410083, China）
Abstract:The effect of minor Ge on susceptibility to stress corrosion cracking (SCC) of 7020 aluminium alloy sheet was investigated by slow strain rate tensile (SSRT) test, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The reason for the decreased strength of 7020-Ge sheet was discussed according to the change of the size and volume fraction of η′ strengthening phase inside grains, and the reason for the decreased SCC susceptibility was discussed according to the change of grain structure, and the size, spacing, chemical compositions of η phase at grain boundaries caused by Ge addition. The results show that, after the introduction of Ge, the ultimate strength of sheets subjected to SSRT test decreases; moreover, the decrement of strength and elongation in NaCl solution compared with air decreases, and ISSRT decreases from 0.059 to 0.017, indicating significantly decreased SCC susceptibility.
Key words: 7020 aluminium alloy; Ge; Stress corrosion cracking; microstructure
