Understanding plastic instability in next generation magnesium alloys

• Applicants: Dr.-Ing. Talal Al-Samman; Dr. Dietmar Letzig
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 420149269

The driver behind the motivation of the project is the global trend towards light-weighting of automotive structures to tackle CO2 emissions and produce an efficient low carbon vehicle technology. In this regard, the development of highly formable wrought Mg alloys requires new optimization strategies to combine the processing and material response in the best way possible. Because significant knowledge gaps still exist in this context, both from fundamental and practical point of views, the aim of the current research is to achieve a comprehensive understanding of the complex microstructure response to mechanical loading under conditions, where the material undergoes PLC-type plastic instability. The findings during the first project period clearly demonstrated that this cannot be established without a collective investigation of multiple materials physics phenomena occurring at different length scales. The project objectives for the second project period build upon the previous ones in probing the mechanistic origin of plastic instability in magnesium alloy candidates for high formability and controlling the microstructure, texture and mechanical response through purposeful addition of alloying elements. The central aims focus on establishing a link between the local structural and chemical properties of precipitates and solute clusters and the susceptibility to plastic instability during deformation at different processing parameters. They also target a synergistic approach of combined solute additions, using a well-informed alloying strategy for designing microstructures with a desired impact on the deformation behavior. Moreover, the project aims envisage expansion of the scope of previous work in new research directions comprising new promising alloy systems and transfer of knowledge to more realistic and complex stress-states occurring during sheet processing. This will enable future development of safe sheet metal forming windows and accelerate the design and development of highly formable wrought magnesium alloys. The proposed objectives and work program strongly benefit from the unique synergy between the participating research teams in Aachen (RWTH-IMM) and Geesthacht (Hereon) regarding the scientific concepts, highly specialized methods and correlative use of several techniques across all relevant length scales. We are confident that the current research proposal constitutes a topical and ambitious challenge with high potential to expand our current understanding of the addressed phenomena and ultimately provide the guidelines to tailor the microstructure and optimize the processing routes of next generation magnesium alloys for an excellent balance of properties.

• DFG Programme: Research Grants