不同取向7050铝合金试样的晶间腐蚀动力学

7050铝合金在使用中易发生晶间腐蚀,不同取向存在差异。采用光学金相显微镜、扫描电镜研究了60mm厚7050铝合金板材不同取向试样的组织分布、晶间腐蚀行为。结果表明:晶粒沿板材轧制方向呈扁平状,晶界处呈链状分布的第二相;晶间腐蚀开始于晶界的第二相处,L(纵向)-T(横向)面的晶界腐蚀后容易呈片状脱落,晶间腐蚀最大深度值最小,为3级晶间腐蚀;T-S(短横向)面和L-S面存在较多晶界,腐蚀容易向深度方向发展,T-S面的晶间腐蚀最大深度最大,为4级晶间腐蚀;腐蚀失重表明,T-S面的腐蚀失重最大,有较多的腐蚀产物脱落。此外,得到了不同取向试样的腐蚀失重和最大腐蚀深度随时间变化规律,并拟合得到了晶间腐蚀动力学方程。

Intergranular Corrosion Dynamics of Different Oriented 7050 Aluminum Alloy

For 7050 aluminum alloy, the intergranular corrosion is apt to occur during use, and there are differences in the corrosion phenomena with varing its sampling directions. In this paper, the tissue distribution and the intergranular corrosion performance of different orientation 7050 aluminum alloy samples with the thickness of 60 mm were investigated using the optical microscope and the scanning electron microscope. Results show that the grains along the sheet rolling direction are flat and present the second phase chain distribution around the grain boundaries, and the intergranular corrosion starts from the second phase of the grain boundaries. The grain boundaries of the LT side after corrosion are easy to exfoliate, and the maximum intergranular corrosion depth is the minimum, belonging to the third level intergranular corrosion. For the TS and LS sides, since there are more grain boundaries after corrosion, the corrosion reaction is prone to develop towards the depth direction, and the intergranular corrosion depth of the TS side is the maximum, belonging to the fourth level intergranular corrosion. The corrosion weight loss of the TS side sample is maximum, which indicates that there are more corrosion products exfoliated. For different orientation sampling specimens, the laws of the corrosion weight loss and the maximum corrosion depth varying with the time are obtained, and the intergranular corrosion kinetics equations are presented after fitting.