Microstructure- and mechanism-correlated characterization of the corrosion fatigue behavior of the creep-resistant magnesium alloys DieMag422 and AE42

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For a safe and efficient use of magnesium alloys in industrial applications, particularly in automotive industry, a high creep and fatigue strength with a sufficient corrosion resistance is necessary. Materials, used e.g. for gearboxes and crankcases, have to withstand loadings at temperatures of up to 200 °C. The creep resistance can be improved by the addition of particular alloying elements which causes a precipitation of intermetallic phases. However, these alloying elements form micro-galvanic cells in the material which can result in a decrease of the corrosion resistance of magnesium alloys. These corrosive stresses, in turn, reduce the lifetime under cyclic loadings. Therefore, the interdependency between chemical composition, creep resistance, corrosion resistance and fatigue strength has to be known to improve material and component properties. For a reliable design and lifetime calculation of magnesium components, both corrosive and cyclic loadings have to be considered to evaluate the influence of these simultaneous loadings on the material properties mechanism-oriented. Current studies deal with the influence of corrosion on the fatigue behavior, but there are no application-optimized and especially time- and cost-efficient testing concepts provided.In the proposed research project, the influence of corrosion on the fatigue behavior will be investigated in-situ using two creep-resistant magnesium alloys DieMag422 und AE42. For a comparative characterization of the corrosion fatigue behavior, a new testing strategy is applied which provides detailed information by using an application-optimized physical and electrochemical sensor system and microstructural investigations with an economical number of tests. The obtained results will be used for the development of a model-based correlation interpreting the corrosion-microstructure-property-relationship quantitatively and qualitatively. Based on the corrosion and fatigue behavior, the model will be used to reliably estimate the fatigue strength and lifetime performance taking into account the corrosive loadings.