(1. 中南大学 轻合金研究院，长沙 410083;
2. 中南大学 材料科学与工程学院，长沙 410083;
3. 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)
摘 要: 7020铝合金经470 ℃固溶1 h后分别进行自然时效0 h、168 h以及65 ℃预时效72 h、168 h，再进行(90 ℃，8 h)+(160 ℃，14 h)双级时效。采用室温拉伸、慢应变速率拉伸(SSRT)、扫描电镜(SEM)、透射电镜(TEM)研究预时效工艺对7020铝合金的常温拉伸性能、抗应力腐蚀性能与显微组织的影响。结果表明:经65 ℃、168 h预时效处理后，合金具有最高的抗拉强度Rm=397.4 MPa和最好的抗应力腐蚀性能ISSRT=-0.003; 65 ℃、72 h预时处理效和自然时效168 h后合金的抗拉强度和抗应力腐蚀性能相当，Rm、ISSRT分别为387.6 MPa、0.034和392.0 MPa、0.036;而直接双级时效合金的抗拉强度和抗应力腐蚀性能最差，Rm、ISSRT为368.9 MPa、0.038。晶内析出相η′(MgZn2)的尺寸随预时效时间的延长而减小，晶界析出相η(MgZn2)的断续分布程度随预时效时间延长而增大。
关键字: 7020铝合金;预时效;拉伸性能;慢应变速率拉伸;显微组织
（1. Light Alloy Research Institute, Central South University, Changsha 410083, China;
2. School of Material Science and Engineering, Central South University, Changsha 410083, China;
3. Key Laboratory of Nonferrous Materials Science and Engineering,
Ministry of Education, Central South University, Changsha 410083, China）
Abstract:After solution heat treatment at 470℃ for 1h, the alloys were natural aged for 0 h or 168 h and pre-aged at 65 ℃ for 72 h or 168 h, respectively. And then, the two-step aging ((90 ℃, 8 h)+(160 ℃, 14 h)) was conducted on these alloys. The effect of pre-ageing treatment on the tensile properties, resistances to stress corrosion and microstructures of 7020 aluminum alloy was investigated by tensile test, slow strain rate tensile (SSRT) test, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). 7020 aluminum alloy aged at 65 ℃ for 168 h pre-ageing treatment has the highest tensile property Rm of 397.4 MPa as well as the best stress corrosion resistance ISSRT of -0.003. The tensile property and stress corrosion resistance of alloy pre-ageing treatment at 65 ℃ for 72 h are 387.6 MPa and 0.034. And it is comparable of that of natural aging 168h, with Rm of 392.0 MPa and ISSRT of 0.036. While the tensile property and stress corrosion resistance of alloy by direct two-step aging are the worst, with Rm of 368.9 MPa and ISSRT of 0.038. With the increase of the pre-aging time, the size of intragranular precipitates η′(MgZn2) inside grains decreases, the intermittent distribution degree of precipitates intragranular precipitates η′(MgZn2) inside grains decreases and the intermittent distribution degree of precipitates η(MgZn2) at the grain boundaries increases.
Key words: 7020 aluminum alloy; pre-aging; tensile property; slow strain rate tensile; microstructure
