CORROSION FATIGUE OF A PRECIPITATION-HARDENED AL-LI-ZR ALLOY IN A 0.5-M SODIUM-CHLORIDE SOLUTION

Corrosion fatigue (CF) experiments have been performed on a high-purity Al-2.5Li-0. 12Zr alloy in a deaerated 0.5 M sodium chloride solution as a function of aging time. The results of these tests were compared to the results of fatigue tests performed in dry air to investigate the effect of aging on the CF susceptibility of the alloy. It was found that the high cycle fatigue strength of the alloy was dramatically reduced by the aqueous environment. Examinations of the relative fatigue strength (DELTA-sigma(Nacl)/DELTA-sigma(air)) indicated that the underaged (UA) alloys were more susceptible to CF than the overaged (OA) alloys over the stress ranges studied, but the difference of the susceptibility between the UA and the OA alloys was reduced by decreasing the applied cyclic stress. The evidence suggests that, for the UA Al-Li-Zr alloys, the CF resistance is determined by both slip-enhanced dissolution and hydrogen embrittlement at high stress ranges, while at low stress ranges, the CF life is predominantly controlled by pitting-induced crack initiation regardless of the aging condition of the alloy.