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采用断面金相法和局部交流阻抗技术对高强度航空铝合金7B04在连续盐雾腐蚀试验下的点蚀行为进行分析。试验结果表明,合金表面点蚀呈现腐蚀速度快速憎加,到腐蚀中期减缓,后期又急剧增加的趋势;但最大点蚀深度始终呈线性增长,点蚀坑的形成机理主要有:阴极相粒子周围基体的溶解、铝本身的去合金化及腐蚀残留物Cu粒子的二次点蚀,其中AlCu和AlCuMg第二相粒子阴极相是其点蚀形成的诱因。局部交流阻抗技术可以提供微小区域阻抗变化的有效信息,适合用于研究点蚀发展的溶解动力学。
The pitting corrosion behavior of high strength aviation aluminum alloy 7B04 under continuous salt spray corrosion test was analyzed by cross-sectional metallographic method and local AC impedance technique. The experimental results show that the corrosion rate of alloy surface shows a rapid increase of corrosion rate, which slows down to the middle of corrosion and increases sharply in the late stage. However, the maximum pitting depth always increases linearly. The formation mechanism of pits mainly includes: The dissolution of the matrix, the de-alloying of the aluminum itself and the secondary pitting corrosion of the Cu particles of the corrosion residue, wherein the cathode phase of the second phase particles of AlCu and AlCuMg is the inducement of pitting corrosion. Local AC impedance technology can provide effective information on impedance changes in small areas and is suitable for studying the dissolution kinetics of pitting development.