(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083；
2. 電子封裝與先進(jìn)功能材料重點(diǎn)實(shí)驗(yàn)室，長沙 410083；
3. 中國電子科技集團(tuán)公司 第三十八研究所，合肥 230088)
摘 要: 采用掃描電鏡(SEM)、電子背散射衍射技術(shù)(EBSD)和透射電鏡(TEM)、慢應(yīng)變速率拉伸和斷裂韌性試驗(yàn)等對峰值時(shí)效和過時(shí)效的7056合金和7095合金組織、力學(xué)性能和應(yīng)力腐蝕開裂敏感性進(jìn)行研究。結(jié)果表明：兩種合金固溶后都發(fā)生了明顯的再結(jié)晶，且7095合金再結(jié)晶程度更高。兩種合金經(jīng)峰值時(shí)效晶內(nèi)都存在尺寸細(xì)小、密度高的析出相，且7056合金晶內(nèi)析出相平均尺寸更小(3.5 nm)、密度更高，表現(xiàn)出更高的強(qiáng)度(643MPa)。兩種合金經(jīng)過時(shí)效晶內(nèi)析出相都發(fā)生明顯粗化，尤其是7095合金晶內(nèi)存在更多的粗大η相，導(dǎo)致7095-T74合金的強(qiáng)度降低8.5%。7056合金和7095合金經(jīng)峰值時(shí)效斷裂韌值分別是26.8 MPa·m1/2和28.2 MPa·m1/2，過時(shí)效后分別增加到29.6 MPa·m1/2和34.7 MPa·m1/2。過時(shí)效的7095合金較高的斷裂韌性是由于晶內(nèi)和晶界強(qiáng)度差減小、晶界存在粗大不連續(xù)的析出相和無沉淀析出帶的共同作用。峰值時(shí)效后，晶界上呈連續(xù)分布的析出相使7056合金和7095合金應(yīng)力腐蝕開裂敏感性較高；過時(shí)效后，晶界析出相呈粗大、不連續(xù)分布，使得合金的SCC敏感性降低。
關(guān)鍵字: 7xxx系鋁合金；時(shí)效析出；應(yīng)力腐蝕開裂；斷裂韌性
（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
