Mechanism-based characterization of the texture influence on the corrosion and corrosion fatigue properties of zinc-based wrought magnesium alloys

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The proposal aims to investigate the damage mechanisms of RE- and Ca-containing extruded Mg-Zn alloys under cyclic loading in air and corrosive media. The results of previous work allow the conclusion that RE- and Ca-containing extruded Mg alloys have the potential of significantly improved properties under fatigue loading and stress corrosion cracking (SCC) conditions compared to the Al-containing Mg standard alloys. By adding suitable alloying elements and setting suitable extrusion parameters, Mg alloys with fine grain sizes and simultaneous texture weakening are to be produced, i.e. by changing the deformation mechanism, properties such as formability, increased fatigue strength, increased corrosion resistance and reduced subcritical crack propagation are to be combined. The formation of twins shall be reduced, not only by weak textures and fine grain sizes but also by homogeneous grain size distributions and suitable precipitates which reduce the formation of twins and at the same time do not hinder the slipping processes. By increasing the fatigue strength on the one hand and the corrosion resistance, on the other hand, the aim is also to achieve a significant improvement of the resistance to SCC. The different processing parameters and the resulting microstructure are to be investigated for their influence on the damage mechanisms under cyclic loading in air and under SCC conditions, and a fundamental process-microstructure-property relationship is to be derived from the findings. By correlating the course of the stress-strain hystereses with the microstructural changes, the complex interaction of the texture, the resulting anisotropy, and the tension-compression asymmetry under cyclic loading in the corrosive medium is to be characterized. The understanding of the process-microstructure-property relationships allows the development of a new group of high-performance extruded Mg alloys and the knowledge transfer to the fatigue and corrosion behavior of Mg sheet alloys in general, which forms a basis for sheet alloy development through cast rolling. Although the topic has a high scientific and economic potential, it has not been investigated yet, nor have the present damage mechanisms been researched regarding the texture influence on fatigue behavior and in particular the SCC.