Influence of Corrosion Damage on Fatigue Behaviour of AZ31 Magnesium Alloy

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The fatigue behaviour of bare and pre-corroded AZ31 magnesium alloy in the stress amplitude control mode was studied. Two sets of test specimens were exposed to corrosion environment prior to fatigue test. Corrosion of test specimens was carried out in a spray of neutral 5% solution of sodium chloride for period of 480 and 1000 hrs. In order to assess the corrosion rate and corrosion mechanism of experimental material, reference specimens were exposed to corrosion environment for period of time ranging from 1 to 1000 hrs. Fatigue tests in the stress amplitude control mode were carried out on smooth and pre-corroded specimens. Analysis of hysteresis curves was preformed. Comparison of cyclic deformation curves showed that cyclic deformation response is not affected by corrosion damage. Experimental data in both, the low and high cycle fatigue regions were fitted by means of regression functions. S-N curves exhibited smooth transition from the low to the high cycle fatigue regions. Presence of corrosion damage resulted in decrease in fatigue life by 23 % (480 hrs) and 42 % (1000 hrs) compared to the smooth specimens. Furthermore, metallographic and fractographic analysis were performed. In the smooth specimens, fatigue cracks initiated from the specimen surface or at inclusions. In the pre-corroded specimens, corrosion damage served as initiation site.

magnesium alloy, corrosion, fatigue

HORYNOVÁ, M.; MODRÁČKOVÁ, I.; DOLEŽAL, P.; GEJDOŠ, P.; ZAPLETAL, J.

21. 5. 2013

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