Texture-dependent crack growth in a wrought magnesium alloy under VHCF conditions

• Applicants: Professor Dr.-Ing. Adrian Rienäcker, since 3/2022; Professorin Dr.-Ing. Martina Zimmermann
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 461909134

The project focuses on the characterization of fatigue crack growth in the threshold range, i.e. in the range of small load amplitudes, a load scenario in which a significant interaction between the material microstructure and the developing crack path can be expected even for a technical crack. Using the AZ31 magnesium alloy available as a rolled semi-finished product, both the orientation of the unit cells and the grain elongation induced by rolling as well as primary precipitates oriented in a preferred direction are considered with regard to the original microstructure. Of particular interest here are the mechanisms of plastic deformation such as basal sliding, pyramidal sliding and the formation of twins, which occur in the crack tip area during fatigue. The test procedure is chosen in such a way that a constant value for deltaK in the range of the threshold value is set during the crack growth, so that the fatigue crack "wanders" through the microstructure with a plastic zone of a given size, thereby addressing different microstructural configurations with regard to the texture influence. The influence of the microstructural features is characterized by the crack growth rate, the crack path and the structural change in the crack tip area. In terms of method, classic resonance fatigue and ultrasonic fatigue testing technology are used in combination with in-situ crack growth measurements using a far-field microscope. Information about the deformation processes at the crack tip, e.g. the identification of the rotational components, provide software-supported analyzes of the lattice distortion in connection with in-situ experiments in the SEM using a micro-tension module. Finally, the results are used to derive basic knowledge about crack propagation rules at very low load amplitudes that can be transferred to other hdp alloys.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr.-Ing. Frank Zeismann, until 3/2022