Effect of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy  

断续时效对7A75铝合金力学性能和抗腐蚀性能的影响

作　　者：Xian-wen YANG Ling-ying YE Yong ZHANG Quan-shi CHENG 杨献文;叶凌英;张勇;程全士(中南大学材料科学与工程学院,长沙410083;航天精工股份有限公司,天津300300)

机构地区：[1]School of Materials Science and Engineering,Central South University,Changsha 410083,China [2]Aerospace Precision Production Co.,Ltd.,Tianjin 300300,China

出　　处：《Transactions of Nonferrous Metals Society of China》2024年第8期2415-2430,共16页中国有色金属学报（英文版）

基　　金：the Tianjin Key Laboratory of Fastening and Connection Technology Enterprises 2022—2023,China(No.TKLF2022-02-C-02);the technical support from the School of Materials Science and Engineering,Central South University,China.

摘　　要：The effects of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy extruded bar were investigated through various analyses,including electrical conductivity,mechanical properties,local corrosion properties,and slow strain rate tensile stress corrosion tests.Microstructure characterization techniques such as metallographic microscopy,scanning electron microscopy(SEM),and transmission electron microscopy(TEM)were also employed.The results indicate that the tensile strength of the alloy produced by T6I6 aging is similar to that produced by T6I4 aging,and it even exceeds 700 MPa.Furthermore,the yield strength increases by 52.7 MPa,reaching 654.8 MPa after T6I6 aging treatment.The maximum depths of intergranular corrosion(IGC)and exfoliation corrosion(EXCO)decrease from 116.3 and 468.5μm to 89.5 and 324.3μm,respectively.The stress corrosion factor also decreases from 2.1%to 1.6%.These findings suggest that the alloy treated with T6I6 aging exhibits both high strength and excellent stress corrosion cracking resistance.Similarly,when the alloy is treated with T6I4,T6I6 and T6I7 aging,the sizes of grain boundary precipitates(GBPs)are found to be 5.2,18.4,and 32.8 nm,respectively.The sizes of matrix precipitates are 4.8,5.7 and 15.7 nm,respectively.The atomic fractions of Zn in GBPs are 9.92 at.%,8.23 at.%and 6.87 at.%,respectively,while the atomic fractions of Mg are 12.66 at.%,8.43 at.%and 7.00 at.%,respectively.Additionally,the atomic fractions of Cu are 1.83 at.%,2.47 at.%and 3.41 at.%,respectively.通过电导率、力学性能、局部腐蚀性能和慢应变速率拉伸应力腐蚀等性能测试,结合金相显微镜、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等显微组织表征方法,研究不同断续时效工艺对7A75铝合金挤压棒材力学性能和抗腐蚀性能的影响。结果表明:合金经T6I6处理后,其抗拉强度与T6I4时效合金的相当,甚至超过700 MPa,屈服强度提高了52.7 MPa,达到654.8 MPa;最大晶间腐蚀和剥落腐蚀深度分别从116.3和468.5μm下降至89.5和324.3μm;应变腐蚀因子从2.1%下降至1.6%。同时获得了高强度与高耐应力腐蚀开裂性能。同样,当合金经T6I4、T6I6和T6I7处理后,晶界析出相的尺寸分别为5.2、18.4和32.8 nm,基体析出相的尺寸分别为4.8、5.7和15.7 nm;晶界析出相中Zn的原子分数分别为9.92%、8.23%和6.87%,Mg的原子分数分别为12.66%、8.43%和7.00%;Cu的原子分数分别为1.83%、2.47%和3.41%。

关 键 词：7A75 aluminum alloy interrupted aging aging precipitation behavior mechanical properties intergranular corrosion exfoliation corrosion stress corrosion cracking 

分 类 号：TG156.92[金属学及工艺—热处理] TG146.21[金属学及工艺—金属学]