(1. 常州大學(xué) 材料科學(xué)與工程學(xué)院，常州 213164；
2. 常州大學(xué) 江蘇省材料表面科學(xué)與技術(shù)重點(diǎn)實(shí)驗(yàn)室，常州 213164；
3. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 采用維氏硬度計(jì)和加速腐蝕試驗(yàn)，分別測(cè)試Al-1.1Mg-1.2Si-0.9Cu合金(質(zhì)量分?jǐn)?shù)，%)在220 ℃時(shí)效過程中硬化行為和IGC敏感性。結(jié)果表明：合金在過時(shí)效階段能夠發(fā)生IGC→PC→IGC的腐蝕行為轉(zhuǎn)變，出現(xiàn)所謂的PC→IGC再敏化現(xiàn)象。過時(shí)效階段晶界Q相出現(xiàn)連續(xù)→斷續(xù)→連續(xù)的分布特征變化，決定其與無析出區(qū)能否構(gòu)成連續(xù)腐蝕微電池，是合金發(fā)生IGC→PC→IGC轉(zhuǎn)變的主要原因。利用晶界析出相粗化與長大過程同步進(jìn)行、先后主導(dǎo)的觀點(diǎn)能夠合理地解釋晶界Q相分布特征和無析出區(qū)寬度在過時(shí)效階段的變化規(guī)律。
關(guān)鍵字: Al-Mg-Si-Cu合金；過時(shí)效；析出；晶間腐蝕；坑蝕
（1. School of Materials Science and Engineering, Changzhou University, Changzhou 213164, China;
2. Jiangsu Key Laboratory of Materials Surface Science and Technology, Changzhou University, Changzhou, 213164, China;
3. School of Materials Science and Engineering, Central South University, Changsha, 10083, China）
Abstract:Based on the Vickers hardness measurement and acceleration corrosion test, the hardening behavior and IGC susceptibility of an Al-1.1Mg-1.2Si-0.9Cu alloy (mass fraction, %) aged at 220 ℃ were investigated. The results show that the corrosion behaviors change in the sequence of IGC→PC→IGC during over-ageing of the peak-aged alloy, which verifies the re-sensitization to IGC. The transmission electron microscopy observation results indicate that the continuous→discontinuous→continuous distribution of grain boundary Q phase precipitates determines whether the continuous electrochemical microcouples can form along the grain boundaries, which is responsible for the transition of IGC→PC→IGC further. Furthermore, a mode of synchronous development and successive domination for coarsening and growth is proposed to explain reasonably the distribution of grain boundary Q phase precipitates and width of precipitate free zones during over-ageing.
Key words: Al-Mg-Si-Cu alloys; over-ageing; precipitation; intergranular corrosion; pitting corrosion
