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Lecture

Corrosion fatigue assessment of creep-resistant magnesium alloys DieMag422 and AE42 using electrochemical responses

Wednesday (08.11.2017)
12:40 - 13:00
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Due to their low density, beneficial strength to weight ratio and good castability, magnesium alloys are very attractive for lightweight applications, e.g. in automotive industry. Especially creep-resistant magnesium alloys offer the possibility for applications in the engine area of automobiles, such as gearboxes and crankcases. However, in such applications in the outer area of automobiles the materials are potentially exposed to corrosive loads. Therefore, their application range for such components is still strongly limited due to their low corrosion resistance, which also impairs the structural integrity under combined corrosive and fatigue loads.

For automotive applications in the engine area materials have to withstand loadings at temperatures up to 200°C, which additionally requires a good creep resistance. Currently available alloys for application temperatures up to 300°C often contain rare earth elements as alloying elements and are therefore relatively expensive. As a result, extensive research has been carried out over the last years to develop low priced creep-resistant magnesium alloys free from rare earth elements. In this context, the creep-resistant magnesium alloy DieMag422 was recently developed, whose improved creep behavior is achieved by the addition of alkaline earth elements Ba and Ca.

In the present study, the influence of corrosion on the microstructure and the dependent mechanical properties under cyclic load for the newly developed creep-resistant magnesium alloy DieMag422 and the rare earth containing alloy AE42 was characterized by means of single and multiple step tests in sodium chloride solutions using corrosion potential and strain measurements. The investigations aimed at a mechanism-oriented description and evaluation of corrosion fatigue cracking in dependence of the cyclic stresses and corrosive loads.

Microstructural deterioration processes could be monitored on the basis of characteristic corrosion potential responses, which were investigated in detail by means of combined oscillation analysis of corrosion potential and total strain oscillations. Correlation between stress amplitudes and corrosion potential responses could be used for a quantitative estimation of the corrosion fatigue behavior.

 

Speaker:
Dr.-Ing. Martin Klein
TU Dortmund University
Additional Authors:
  • Gerrit Frieling
    TU Dortmund University
  • Prof. Dr. Frank Walther
    TU Dortmund University

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