(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 电子封装与先进功能材料重点实验室，长沙 410083；
3. 中国电子科技集团公司 第三十八研究所，合肥 230088)
摘 要: 采用扫描电镜(SEM)、电子背散射衍射技术(EBSD)和透射电镜(TEM)、慢应变速率拉伸和断裂韧性试验等对峰值时效和过时效的7056合金和7095合金组织、力学性能和应力腐蚀开裂敏感性进行研究。结果表明：两种合金固溶后都发生了明显的再结晶，且7095合金再结晶程度更高。两种合金经峰值时效晶内都存在尺寸细小、密度高的析出相，且7056合金晶内析出相平均尺寸更小(3.5 nm)、密度更高，表现出更高的强度(643MPa)。两种合金经过时效晶内析出相都发生明显粗化，尤其是7095合金晶内存在更多的粗大η相，导致7095-T74合金的强度降低8.5%。7056合金和7095合金经峰值时效断裂韧值分别是26.8 MPa·m1/2和28.2 MPa·m1/2，过时效后分别增加到29.6 MPa·m1/2和34.7 MPa·m1/2。过时效的7095合金较高的断裂韧性是由于晶内和晶界强度差减小、晶界存在粗大不连续的析出相和无沉淀析出带的共同作用。峰值时效后，晶界上呈连续分布的析出相使7056合金和7095合金应力腐蚀开裂敏感性较高；过时效后，晶界析出相呈粗大、不连续分布，使得合金的SCC敏感性降低。
关键字: 7xxx系铝合金；时效析出；应力腐蚀开裂；断裂韧性
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Electronic Packaging and Advanced Functional Materials, Central South University, Changsha 410083, China;
3. The 38th Institute of China Electronics Technology Group Corporation, Hefei 230088, China）
Abstract:The microstructure, mechanical properties and stress corrosion cracking sensitivity of 7056 and 7095 alloys with peak aging and over aging treatments were studied by SEM, EBSD, TEM, slow strain rate tensile tests and fracture toughness tests. The results show that both alloys have obvious recrystallization after solid solution and the recrystallization degree of 7095 alloy is higher than 7056 alloy. After peak aging, fine precipitates with small size and high density in both alloys. 7056 alloy has smaller size (3.5 nm) and higher density than 7095 alloy, thus showing higher strength (643 MPa). After overaging, the precipitates of the two alloys obviously coarsen, leading to deteriorative strength. The 7095 alloy have lots of coarsening η phase after overaging, thus the strength of the 7095 alloy decreased 8.5%. The fracture toughness values of 7056 and 7095 alloys after peak aging are 26.8 MPa·m1/2 and 28.2 MPa·m1/2, respectively, and increase to 29.6 MPa·m1/2 and 34.7 MPa·m1/2, respectively, after overaging. The large fracture toughness of overaged 7095 alloy is due to the decrease of the strength difference between the grain and the grain boundary. The combined action of the precipitate free zones and the coarsening and discontinuous grain boundary precipitates is another reason. The continuous precipitates in the grain boundary in the two peak aging alloys result in high stress corrosion cracking (SCC) sensitivity. After overaging, the grain boundary precipitates (GBPs) in the two alloys turn to discontinuous distribution and obviously coarsen, decreasing the SCC sensitivity.
Key words: 7xxx series aluminum alloy; aging precipitation; stress corrosion cracking; fracture toughness
