(中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 采用拉伸性能測試、慢應(yīng)變速率拉伸測試、DSC分析、電導(dǎo)率測試及透射電鏡觀察，研究不同回歸再時(shí)效(RRA)處理制度對7A55鋁合金淬火預(yù)拉伸(W51)板材顯微組織、拉伸性能和抗應(yīng)力腐蝕(SCC)性能的影響。結(jié)果表明：采用120 ℃、24 h預(yù)時(shí)效，180 ℃、60 min回歸處理和120 ℃、24 h終時(shí)效的RRA工藝，可使7A55合金獲得與T6態(tài)相當(dāng)?shù)膹?qiáng)度，而電導(dǎo)率大大提高，抗應(yīng)力腐蝕性能接近T73態(tài)水平。7A55合金經(jīng)適當(dāng)?shù)腞RA處理后，晶內(nèi)保持類似于T6狀態(tài)的顯微組織結(jié)構(gòu)，為細(xì)小、彌散的η′相和極少量的η相；同時(shí)使晶界析出物的大小和分布特征與T73狀態(tài)類似，為呈斷續(xù)、孤立分布的粗化平衡相。
關(guān)鍵字: 7A55鋁合金；回歸處理；再時(shí)效處理；應(yīng)力腐蝕；微觀組織
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of retrogression and reaging (RRA) treatment on the microstructure, tensile properties and resistance to SCC of a pre-stretched 7A55 aluminum alloy plate were studied by tensile test, slow strain rate tensile test, DSC analysis, conductivity measurement and transmission electron microscopy(TEM) observations. The results show that perfect mechanical and stress corrosion resistance properties can be obtained if the alloy is treated by the RRA of 120 ℃, 24 h pre-ageing, 180 ℃, 45 min retrogression and 120 ℃, 24 h re-aging. The strength of the alloy is almost the same compared with the T6 sample, while the conductivity increases greatly, and the stress corrosion resistance property enhances to the levels of T73 condition. Treated by proper RRA, small amount of η and a great mount of fine and dispersive precipitates η′ are observed in the matrix which is similar to that of T6 condition, while the coarse and discontinuous equilibrium precipitates are observed at the grain boundaries which is analogous to that of the T73 condition.
Key words: 7A55 Al alloy; retrogression treatment; reaging treatment; stress corrosion; microstructure
