(北京科技大學 材料科學與工程學院，北京 100083)
摘 要: 采用光學顯微鏡、電子背散射衍射和透射電鏡，研究亞晶界析出演變對7050鋁合金時效過程電導率和沖擊韌性的影響。結果表明：亞晶界上析出相轉變后，在二級時效過程中完成長大過程，并使電導率升高，沖擊韌性降低。時效過程中亞晶界取向差增大，有利于η′相在亞晶界形核。一級時效升溫至二級時效使亞晶界η′相轉變?yōu)棣窍啵译妼噬?3.04%，沖擊韌性降低53.91%。二級時效過程中，亞晶界η相持續(xù)轉變長大、無析出自由區(qū)寬化以及晶內析出量增加，導致電導率升高，沖擊韌性降低。統(tǒng)計Graff試劑侵蝕金相中的晶界長度演變確定亞晶界η相的轉變長大完成過程為(121 ℃, 360 min)+(177 ℃, 60 min)。
關鍵字: 7050鋁合金；亞晶界析出；時效；電導率；沖擊韌性
（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
