(1. 湖南省產(chǎn)商品質(zhì)量監(jiān)督檢驗(yàn)研究院，長(zhǎng)沙 410007；
2. 湖南省特種設(shè)備檢驗(yàn)檢測(cè)研究院，長(zhǎng)沙 410117；
3. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙 410083)
摘 要: 采用慢應(yīng)變速率試驗(yàn)、金相顯微鏡、掃描電鏡、掃描透射電鏡等手段研究350 ℃冷卻至100 ℃時(shí)的冷卻速率從1720 ℃/min減小至30 ℃/min對(duì)7020鋁合金顯微組織和應(yīng)力腐蝕斷裂敏感性的影響。結(jié)果表明：NaCl溶液中拉伸的強(qiáng)度和伸長(zhǎng)率較空氣中的都更低，抗拉強(qiáng)度下降率隨冷卻速率減小而增加，但伸長(zhǎng)率下降率先減小再增加。冷卻速率減小，應(yīng)力腐蝕指數(shù)ISSRT增加，合金的應(yīng)力腐蝕斷裂敏感性升高。通過(guò)冷卻速率減小時(shí)晶界第二相尺寸、間距、化學(xué)成分及無(wú)沉淀析出帶寬度和成分的變化來(lái)分析和探討應(yīng)力腐蝕斷裂敏感性增加的原因。
關(guān)鍵字: 7020鋁合金；冷卻速率；應(yīng)力腐蝕斷裂；顯微組織
（1. Hunan Testing Institute of Product and Commodity Supervision, Changsha 410007 China;
2. Hunan Special Equipment Inspection and Testing Research Institute, Changsha 410117 China;
3. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of cooling rate decreasing from 1720 ℃/min to 30 ℃/min through 350-100 ℃ on microstructure and susceptibility to stress corrosion cracking (SCC) of 7020 aluminium alloy were investigated by slow strain rate test, optical microscopy, scanning electron microscopy and scanning transmission electron microscopy. The results show that the strength and elongation of specimens tested in NaCl solution are lower than that tested in air, the strength decrement tends to increase with the decrease of cooling rate, while the elongation decrement tends to decrease first and then increase. SCC susceptibility increases with the decrease of cooling rate as a lower cooling rate results in a larger ISSRT. The reason was discussed according to the change of the size, spacing, chemical compositions of second phase at grain boundaries and width and chemical compositions of precipitates free zones adjacent to grain boundaries caused by the decrease of cooling rate.
Key words: 7020 aluminium alloy; cooling rate; stress corrosion cracking; microstructure
