高速列车A7N01P-T4铝合金焊接接头腐蚀行为研究

Corrosion Behavior of Weld Joints of Aluminum Alloy A7N01P-T4 for High-speed Trains

选取高速列车用A7N01P-T4铝合金及其焊接接头进行中性盐雾实验,研究了其在实际应用中未去包铝层情况下的盐雾腐蚀失效行为。结果表明,盐雾腐蚀过程中焊缝腐蚀最严重,其次是热影响区,母材腐蚀最轻;腐蚀过程起源于包铝层的点蚀,随实验时间的延长腐蚀坑变密并扩大,甚至相互交错连结成片。A7N01-T4焊接接头的腐蚀产物主要有O,Al和C;比较带有包铝层的母材、焊缝区以及去除包铝层的母材三者的极化曲线,其自腐蚀电位负向依次增加,腐蚀电流密度依次增大,从极化曲线也可得出三者的耐腐蚀性能依次降低,包铝层对于铝合金基体以及焊接接头的热影响区起到了较好的防护作用。

The corrosion behavior of the pure Al clad alloy A7N01P-T4 and its welding joints for conventionally making high speed train,was studied by means of neutral salt spray corrosion tests. The results showed that the corrosion of the welding line was the most serious, the heat affected zone next, and the base metal was most slight. The corrosion process originated in pits on the aluminum clad. Meanwhile both the density and dimension of the pits increased with time, they even connected with each other to form large ulcer-like area. Energy dispersive spectroscopy and infrared spectrum showed that the corrosion products of A7N01P-T4 consisted of three elements: O, Al and C. The measurement of polarization curves proved that the free corrosion potentials negatively shift and the corrosion currents increase following a serie: the base alloy with Al clad, the weld zone and the base alloy without Al clad, in other words, of which the corrosion resistance decreased in the same direction. It is believed that the Al clad may be beneficial to enhancement of the corrosion performance of the matrix and the heat affected zone of A7N01P-T4.