Corrosion fatigue acoustic emission characteristics and evaluation of friction stir welding joints of AZ31 magnesium alloy in 3.5 wt.% NaCl solution

Acoustic emission (AE) technology is adopted to monitor the whole corrosion fatigue behavior of AZ31 welded joints in 3.5 wt.% NaCl solution. Characteristics of AE signals, effect of corrosive environment and corrosion fatigue evaluation are analyzed and discussed. Results show that the AE waveform has periodic characteristics reflecting the sinusoidal fatigue loading law and the peak frequency of burst waveforms mainly concentrates at about 150 kHz. The steady accumulated energy of AE, ΔEas, is believed to be the boundary estimating the fatigue limit of the material. The corrosion fatigue limit of AZ31 welded joints in 3.5 wt.% NaCl solution is 45.05 MPa, which is consistent well with that obtained by S–N curve, 41.53 MPa. AE technology, which has the advantage of penetrating corrosive media, is effective for evaluating corrosion fatigue limit of AZ31 welded joints in corrosive environment. Corrosion fatigue estimation model of two-line not three-line could be used due to that the corrosive environment makes the deformation process of corrosion fatigue in each stage accelerate or even disappear.