(1. 中南大學 材料科學與工程學院，長沙 410083；
2. 湖南城市學院 土木工程學院，益陽 413000)
摘 要: 采用透射電鏡分析、力學拉伸性能測試和電導率測試， 研究不同回歸再時效（RRA）處理制度對含Sc超高強Al-Zn-Mg-Cu-Zr合金組織與性能的影響。結果表明：采用120 ℃，24 h預時效+180 ℃，30 min回歸處理+120 ℃，24 h終時效的RRA處理工藝，可以使合金獲得理想的力學性能和抗應力腐蝕性能；與T6態(tài)相比，該工藝獲得的合金強度僅略微下降，而電導率則大大提高；含Sc超高強Al-Zn-Mg-Cu-Zr合金經RRA處理后，晶內含大量均勻細小的η′相和少量的η平衡相，合金晶界處的平衡相粗化明顯，呈現(xiàn)斷續(xù)、孤立分布；與T6態(tài)處理的合金相比，無沉淀析出帶變寬；其晶內析出相與T6峰值時效態(tài)的類似，晶界組織與雙級過時效態(tài)的組織類似。
關鍵字: Al-Zn-Mg-Cu-Zr合金；Sc；超高強；再時效；力學性能；微觀組織
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Department of Civil Engineering, Hunan City University, Yiyang 413000, China）
Abstract:The effects of retrogression and reaging (RRA) treatment on the microstructures and mechanical properties of super-high strength Al-Zn-Mg-Cu-Zr alloy containing Sc were studied by transmission electron microscopy, tensile and conductivity tests. The results show that perfect mechanical and stress corrosion resistance properties can be gained if the alloy is treated by the RRA heat treatment of 120 ℃, 24 h pre-ageing, 180℃, 30 min retrogression and 120℃, 24 h re-ageing. Compared with the T6 sample, the strength of the alloy decreases slightly while the conductivity increases greatly. Treated by RRA, a great amount of fine and homogenized distributed precipitations η′ and few equilibrium phases η are observed inside the grains, while the equilibrium phases on the grain boundaries coarsen obviously, distributing discontinuously and isolated. The precipitation free zones are broadened than that of the T6 sample. The microstructure inside the grains is similar to that of the T6 sample while the microstructure of the grain boundary is similar to that of the duplex over-aged sample.
Key words: Al-Zn-Mg-Cu-Zr alloy; Sc; super-high strength; re-aging; mechanical properties; microstructure
