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摘要
The intergranular corrosion (IGC) behaviors of Zn free and Zn micro-alloyed Al-3.7Cu-1.15Li-0.5Mg alloys with T6 aging at 150 and 175 degrees C for various time was investigated, and a corrosion diagram associated with aging process was established. The results show that the IGC sensitivity of the Zn microalloyed Al-Li alloy is a little lower than that of the Zn free Al-Li alloy. With aging progress, the corrosion mode changes in the following order: pitting and local IGC (initial aging stage), general IGC (under-aging stage), local IGC (near peak-aging stage) and pitting (over-aging stage) again. With aging time extension, the IGC depth is increased firstly and then decreased. The grain boundary precipitates are coarsened and their spacing is increased with aging process. In addition, the grain potential is decreased due to the precipitation of Ti and theta phases within grains, and the potential difference between grain and grain boundary is therefore lowered. These two factors result in the above IGC sensitivity variation with aging process.
