回归再时效中预时效温度对7050铝合金应力腐蚀性能的影响  

Effect of Pre-aging Temperature in Retrogression and Re-aging Treatment on Stress Corrosion Resistance of 7050 Aluminum Alloy

作　　者：辛星[1] 张新明[1] 刘胜胆[1] 宋丰轩[1] 陈彬[1] 

机构地区：[1]中南大学材料科学与工程学院,长沙410083

出　　处：《材料工程》2014年第5期29-34,共6页Journal of Materials Engineering

基　　金：国家重点基础研究发展计划("973"计划)资助项目(2012CB619501)

摘　　要：采用硬度测试、电导率测试、慢应变速率拉伸、透射电镜和扫描电镜等方法,研究了回归再时效热处理工艺中预时效温度对7050铝合金微观组织和应力腐蚀性能的影响。结果表明:随着预时效温度升高,回归再时效后7050铝合金晶内析出相从以GP区为主转变为以η′相为主,晶界析出相逐渐粗化,晶界变得不连续分布,合金应力腐蚀敏感性降低;但晶界无沉淀析出带宽度增加,120℃时达到140nm,易导致应力集中和阳极溶解,合金抗应力腐蚀性能下降。预时效温度为80℃,即稍微欠时效时,7050铝合金抗应力腐蚀性能较好,在缓慢应变速率(10-6s-1)和3.5%NaCl溶液腐蚀介质下,合金抗拉强度为473.5MPa,伸长率为10.67%,应力腐蚀指数为0.05824。The effect of the pre-aging temperature in retrogression and re-aging （RRA） treatment on stress corrosion resistance of 7050 aluminum alloy was investigated by means of hardness tests, conductivity tests, slow strain rate tensile （SSRT） tests, transmission electron microscopy （TEM） and scanning electron microscopy （SEM）. The results show that when the pre-aging temperature increases, the main intragranular precipitates in 7050 aluminum alloy transform from GP zones to 7/1 phases after RRA. The grain boundary precipitates become coarser and consequently the grain boundary becomes discontinuous, which leads to the reduction of sensitivity of stress corrosion. At the meantime, the precipitate free zone （PFZ） becomes wider, whose width goes up to 140nm when pre-aging tem- perature rises to 120~C, causing stress concentration and anode dissolution which are harmful to the stress corrosion resistance of the alloy. When the pre-aging temperature is 80 ~C, as in under-aged condition at the pre-aging stage of RRA, the alloy shows better stress corrosion resistance. The tensile strength, elongation and stress corrosion index （/SSRT） of the alloy are 473. 5MPa, 10. 67% and 0.05824 with slow strain rate （10^-6 s^-1） and corrosion medium of 3.5 % NaCl solution.

关 键 词：7050铝合金 预时效温度 析出相 应力腐蚀 

分 类 号：TG146.2[一般工业技术—材料科学与工程]