Study on the effect of corrosion on the tensile behavior of an AZ91 alloy

The effect of corrosion on the tensile behavior of an as-cast AZ91 alloy was investigated via systematical experiments. The corrosion residual strength of the AZ91 magnesium alloy is approximately negative linear dependent on the extreme depth of corrosion pit, which was quantitatively obtained by the corrosion morphology analysis and the statistic analysis. Experimental results reveal that the corrosion residual strength of the AZ91 magnesium alloy dropped quickly in the first 40 h due to the initiation and development of the corrosion pit and subsequently decreased slowly as a result of the development of the corrosion pit encountered the beta phase. The beta phase at the grain boundary of the primary a phase acts as an effective barrier to prevent the development of the corrosion pit into the alloy matrix and thus remarkably prevents the drop of the corrosion residual strength. In general, the variation of the corrosion residual strength exhibits an exponential decay regulation within the testing time. Consequently, the empirical prediction of the corrosion residual strength was given with regard to the variation of the corrosion residual strength varied with the immersion time.