李 桓,吴 胜,张宇辉,徐光霈,杨立军
AuthorsHTML:李 桓，吴 胜，张宇辉，徐光霈，杨立军
AuthorsListE:Li Huan,Wu Sheng,Zhang Yuhui,Xu Guangpei,Yang Lijun
AuthorsHTMLE:Li Huan，Wu Sheng，Zhang Yuhui，Xu Guangpei，Yang Lijun
Unit:天津大学天津市现代连接技术重点实验室，天津 300072
Unit_EngLish:Tianjin Key Laboratory of Advanced Joining Technology，Tianjin University，Tianjin 300072，China
Abstract_Chinese:采用 TIG 焊工艺连接 5.3 mm 厚度 2195-T8 铝锂合金对接试板，通过金相显微镜和扫描电镜对 TIG 焊接头 组织进行分析．为研究接头腐蚀行为，进行了 TIG 焊接头晶间腐蚀试验与接头各位置电化学分析．发现在 IGC(晶 间腐蚀)溶液中，焊缝耐蚀性最差，最大腐蚀深度达到 163.9 μm；其次是母材，最大腐蚀深度达到 125.1 μm；热影 响区未出现明显的晶间腐蚀特征，发生了均匀腐蚀，最大深度达到 37.8 μm．在电化学腐蚀中，母材的自腐蚀电流 密度最小，为 1.04 μA/cm2 ；其次是热影响区，自腐蚀电流密度为 3.45 μA/cm2 ；焊缝自腐蚀电流密度最大，达到 5.03 μA/cm2 ．焊缝的开路电位最低，为-0.763 5 VSCE；其次是母材，开路电位为-0.729 3 VSCE；热影响区开路电位 最高，为-0.676 0 VSCE．母材进行电化学腐蚀时，腐蚀速率最低，但在接头中浸入 IGC 溶液中时腐蚀深度大于热影 响区，认为原因有二：一是热影响区-母材、热影响区-焊缝构成了区域腐蚀电偶，热影响区电位最高，作为阴极被 保护，焊缝、母材作为阳极，被加速腐蚀；二是母材晶界第 2 相连续，晶界处有密集细小的 T1 相(Al2CuLi)，第 2 相与周围基体构成腐蚀微电偶，加速了晶界处 A 基与 T1 相的溶解，而热影响区晶界处的第 2 相呈不连续点状，大 多溶解于 Al 基中，不利于腐蚀沿晶界向晶粒深处扩展，同时，第 2 相溶解导致 Al 基 Cu 元素增加，电位升高，Al 基腐蚀倾向降低
Abstract_English:The butt test plate of 2195-T8 Al-Li alloy with a thickness of 5.3 mm was welded by tungsten inert gas(TIG)welding. The microstructure of the TIG-welded joint was analyzed via metallographic microscopy and scanning electron microscopy. To study the joint corrosion behavior，an intergranular corrosion test of the TIG-welded joint and an electrochemical analysis of each joint position were conducted. The results showed that the corrosion resistance of the fusion zone(FZ)，with a maximum corrosion depth of 163.9 μm，was the worst，followed by the base metal(BM)，with a maximum corrosion depth of 125.1 μm. The heat-affected zone(HAZ)did not exhibit sig\u0002nificant intergranular corrosion characteristics and showed uniform corrosion，with a maximum depth of 37.8 μm in the intergranular corrosion(IGC)solution. Through electrochemical corrosion tests，it was found that the BM had the lowest corrosion current density(1.04 μA/cm2)，followed by the HAZ(3.45 μA/cm2)，and the FZ had the high\u0002est(5.03 μA/cm2). Moreover，the FZ had the lowest open-circuit potential(-0.763 5 VSCE)，followed by the BM (-0.729 3 VSCE)，and the HAZ had the highest(-0.676 0 VSCE). When the BM was subjected to electrochemical corrosion，the corrosion rate was the lowest；however，when the joint was immersed in IGC solution，the corrosion depth was greater than that of the HAZ，which is attributed to two reasons. First，the HAZ-BM and HAZ-FZ constitute the regional galvanic corrosion；HAZ acts as the cathode because of its higher open-circuit potential，while theFZ and BM act as the anode and thus undergo accelerated corrosion. Second，the second phase of the grain boundary of the BM is continuous and features a dense and tiny T1 phase；the second phase and surrounding matrix form mi\u0002croscopic galvanic corrosion，which accelerates the dissolution of the grain boundary area；in contrast，the second phase at the HAZ boundary is discontinuous and mostly dissolves in the Al matrix；this is not conducive to the expansion of corrosion along the grain boundaries；moreover，the dissolution of the second phase results in the increase in Cu elements in the Al matrix，and the Al matrix corrosion tends to be lower due to the increase in potential.
Keyword_Chinese:铝锂合金；TIG 焊接头；晶间腐蚀；电化学
Keywords_English:Al-Li alloy；TIG-welded joint；intergranular corrosion；electrochemistry

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