(北京科技大学 材料科学与工程学院，北京 100083)
摘 要: 采用光学显微镜、电子背散射衍射和透射电镜，研究亚晶界析出演变对7050铝合金时效过程电导率和冲击韧性的影响。结果表明：亚晶界上析出相转变后，在二级时效过程中完成长大过程，并使电导率升高，冲击韧性降低。时效过程中亚晶界取向差增大，有利于η′相在亚晶界形核。一级时效升温至二级时效使亚晶界η′相转变为η相，且电导率升高13.04%，冲击韧性降低53.91%。二级时效过程中，亚晶界η相持续转变长大、无析出自由区宽化以及晶内析出量增加，导致电导率升高，冲击韧性降低。统计Graff试剂侵蚀金相中的晶界长度演变确定亚晶界η相的转变长大完成过程为(121 ℃, 360 min)+(177 ℃, 60 min)。
关键字: 7050铝合金；亚晶界析出；时效；电导率；冲击韧性
（School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China）
Abstract:The effects of precipitation evolution at sub-grain boundaries on electrical conductivity and impact toughness of 7050 aluminum alloy during aging were investigated by optical microscopy, electron back scatter diffraction and transmission electron microscopy. The results show that the electrical conductivity increases and the impact energy drops due to the transformation and growth of precipitation. η′ phase prefers to precipitate at sub-grain boundaries as the misorientation increases. At the heating stage between two-step aging, the electrical conductivity rises by 13.04% and impact toughness decreases by 53.91% as transformation from η′ to η. The microstructure evolutions including η phase precipitating at sub-grain boundaries, precipitate spacing increasing and precipitation-free-zone widening improve the electrical conductivity but deteriorate the impact toughness. The length of grain boundaries etched by Graff solution and viewed in the optical microscopy was counted to ensure the transformation and growth of η phase completed at (121 ℃, 360 min)+(177 ℃, 60 min).
Key words: 7050 Al alloy; sub-grain boundary precipitation; aging; electrical conductivity; impact toughness
