Effect of loading conditions on corrosion fatigue process of FSW AA6061-T6 joint in 3.5% NaCl studied by electrochemical noise

Abstract

Electrochemical noise (EN) signals generated during corrosion fatigue (CF) process of friction stir welded (FSW) AA6061-T6 joints in 3.5 wt% NaCl solution under different loading conditions were monitored. Wavelet analysis and cumulative probability calculations showed that the increase in peak stress, stress ratio and stress frequency all lead to a decrease in Rn and an increase in the incubation rate of local events. Under current experimental conditions, the influence of peak stress is the most significant, while the influence of frequency is the least. The combination of EN signal analysis and transmission electron microscopy (TEM) observations indicates that the coarsening of β′ phase and the extensive dissolution of β'' phase are the main reasons for preferential failure in the weakest heat affected zone. The main contribution of this study is preliminary investigating the CF behavior of FSW AA6061 joints under different low cycle fatigue conditions. Moreover, EN is an effective strategy for monitoring CF process and establishes a connection between an alternative EN technique and in-situ CF behavior research.