Effect of Homogenization on the Pitting Corrosion Behavior of Al-Li-Cu Alloys

Effect of homogenization on the pitting corrosing of Al-Li-Cu and Al-Li-Cu-Zr casting alloys were investigated metallurgically and electrochemically. Three types of inclusions, Al-Cu, Al-Fe and Si-rich compounds, were observed among dendrite arms. The only Al-Cu compounds could be solutionized with homogenization at 793K, but remained even after the treatment for 86.4ks. An anodic Al-Cu compound which may be T_2(Al_6Li_3Cu) phase dissolved in the early stage of immersion. For the alloys as-cast or homogenized unitl 0.6ks, the pitting potential changed in the noble direction with the increase of homogenization time, and the pitting attack ocurred preferentially inside of the cored structure with a lower Cu concerntration than outside. On the other hand, the alloys homogenized for the longer time exhibited a nearly constant pitting potential -670mV, and the pitting took place at adjacent region to Al-Fe compound particles.