(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)
摘 要: 采用光學(xué)顯微鏡、X射線衍射、掃描電鏡、透射電鏡、浸泡試驗(yàn)等方法，研究固溶處理(465~490 ℃, 1 h)對(duì)峰值時(shí)效(120 ℃, 24 h)7050鋁合金晶間腐蝕的影響規(guī)律。浸泡結(jié)果表明：隨著固溶處理溫度提高，峰值時(shí)效合金晶間腐蝕敏感性先逐漸降低后又升高，其中，經(jīng)(485 ℃, 1 h)固溶處理的峰值時(shí)效合金的晶間腐蝕抗力顯著提高。微觀組織分析和晶界偏聚建模表明：適當(dāng)提高固溶處理溫度，不僅促進(jìn)S-Al2CuMg相溶解，還增大Cu在晶界偏聚濃度，從而提高峰值時(shí)效合金晶界η-Mg(Zn,Cu)2相中的Cu含量。據(jù)此初步提出：晶界η-Mg(Zn,Cu)2相中Cu含量的增加使其腐蝕電位正移，從而縮小了與無(wú)析出區(qū)的腐蝕電位差，使得二者形成微電偶的傾向性下降，由此造成峰值時(shí)效合金晶間腐蝕敏感性相應(yīng)逐漸降低、甚至消除。至于更高溫度固溶處理的峰值時(shí)效合金再次發(fā)生晶間腐蝕，這與合金發(fā)生過(guò)燒、形成S-Al2CuMg相有關(guān)。
關(guān)鍵字: 7050鋁合金；固溶處理；峰值時(shí)效；晶間腐蝕
（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）
Abstract:The effects of solution-treating temperatures (465-490 ℃, 1 h) on the intergranular corrosion of 7050 Al alloy peak-aged at 120 ℃ for 24 h were investigated by optical microscope, X ray diffraction, scanning electron microscope, transmission electron microscope and accelerated corrosion test. The immersion test indicates that the intergranular corrosion (IGC) susceptibility of the alloy decreases first, and then increases with the solution-treating temperatures increasing. Especially, the IGC resistance can be enhanced significantly for the peak-aged sample solution-treated at 485 ℃. Furthermore, the microstructural observations and grain boundary segregation modeling show that the increase of the solution-treating temperatures leads to the accelerated dissolution of S-Al2CuMg and increases Cu segregation at grain boundaries, and then increases the Cu content of the grain boundary η-Mg(Zn,Cu)2 precipitating in the peak-aged alloy. Based on the above results, it can be proposed preliminarily that the positive shift of the corrosion potential of the corrosion potential of the grain boundary η-Mg(Zn,Cu)2 precipitates due to the increased Cu content shortens the potential difference with the precipitation free zones, which will decrease the tendency to form the grain boundary microcouplings and then reduce, even remove the IGC susceptibility of the alloy. By comparison, the increased IGC susceptibility of the alloy solution-treated at higher temperatures is related to the S-Al2CuMg phase in the eutectics as a result of over-burning.
Key words: 7050 Al alloy; solution treatment; intergranular corrosion
