Four groups of samples

including base metal（BM）

FSW

FSW+T and FSW+T+A samples

were designed to investigate the effects of plastic deformation on the corrosion resistance of the joints immersed in 3.5% NaCl solution.The results reveal that the corrosion resistance of AZ31 magnesium alloy can be enhanced significantly by friction stir welding

while post-welded tension can weaken significantly the corrosion resistance of the joint

however post-annealing treatment can enhance largely the corrosion resistance.Corrosion rate of the four groups of samples is presented as follows:BM>FSW+T>FSW≈FSW+T+A.In addition

both extension twinning and dislocation slip introduced by post-welded tension have an adverse effect on the corrosion resistance of the joint

in which dislocation slip plays the key role.