與性能的影響
( 中南大學(xué) 材料科學(xué)與工程學(xué)院， 長沙 410083)
摘 要: 采用硬度、 電導(dǎo)率測試、 DSC熱分析及TEM觀察等手段， 研究了回歸再時效處理對一種新型低頻電磁鑄造超高強(qiáng)鋁合金組織與性能的影響。研究發(fā)現(xiàn)： 合金在120℃時效24h后具有較高的硬度和強(qiáng)度水平。 合金合宜的回歸再時效處理工藝為120℃、 24h預(yù)時效， 180、 60min回歸， 之后120℃、 24h再時效。 在此條件下， 合金的抗拉強(qiáng)度、屈服強(qiáng)度、 延伸率和電導(dǎo)率（IACS）分別為721MPa、 700MPa、 8.1%和34.5%。 TEM觀察表明： 回歸再時效過程中合金性能的變化與其微觀組織的演變密切相關(guān)；回歸初期， GP區(qū)和η′相的回溶導(dǎo)致合金硬度下降； 隨后， η′和η相的析出使硬度重新上升至峰值； 最后， /η′/相轉(zhuǎn)變成η、 以及η相粗化引起硬度單調(diào)下降；再時效后析出的η′相提高了合金的強(qiáng)度、 硬度和電導(dǎo)率。
關(guān)鍵字: RRA；電磁鑄造； 超高強(qiáng)度； 鋁合金； 微觀組織； 性能
new type ultra high strength aluminum alloy
PAN Qin-lin, ZHOU Chang-rong
（ College of Materials Science and Engineering,
Central South University, Changsha 410083, China）
Abstract: The effect of Retrogression and re-ageing treatments on the microstructure and properties of a new type low frequency electromagnetic casting ultra-high-strength aluminum alloy were investigated using hardness and electric conductivity tests, DSC analysis and TEM observation. It is found that after ageing at 120℃ for 24h, the studied alloy can gain high hardness and strength. After pre-ageing at 120℃ for 24h, retrogression at 180℃ for 60min, and then re-ageing at 120℃ for 24h, the tensile strength, yield strength, elongation and electric conductivity(IACS) of the studied alloy are 721MPa， 700MPa， 8.1% and 34.5% respectively. The TEM observation shows that the property changes of the alloy during RRA are closely related to the microstructural evolution. In the early stage of retrogression, the re-dissolution of GP zone and η′ leads to the decrease of hardness, while precipitation of η′ and η makes hardness increase again to a peak value. Then, the transition of η′→η and coarsening of η lead to the decrease of hardness. Precipitation of η′ after reageing increases the hardness， strength and electric conductivity of the studied alloy.
Key words: RRA; electromagnetic casting; ultra high strength; aluminum alloy; microstructure; property
