In situ diffraction analysis using high energy synchrotron radiation to investigate the influence of active deformation and recrystallisation mechanisms on the microstructural development of new magnesium sheet alloys

• Applicants: Dr. Jan Bohlen; Professor Dr. Heinz-Günter Brokmeier; Professor Dr.-Ing. Sangbong Yi
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 262840495

The formation of microstructure and texture during a rolling process determines the properties of magnesium sheets and their technical potential for lightweight application. Weakening the texture or changing the main texture components as well as grain refinement, result in distinctly increased formability of the sheets. However, such textures lead to enhanced mechanical anisotropy. A high number of individual mechanisms is currently discussed regarding their impact on the microstructure and texture development. Although the analysis reveals altered activation of different deformation mechanisms as well as effects on the recrystallization behaviour during the rolling process, the effect of added rare earth elements or calcium in ternary magnesium alloys on these mechanisms as well as the impact on the microstructure and texture development is not well understood. The aim of this project is to apply in-situ hard X-rays diffraction experiments using synchrotron radiation in order to draw direct conclusions about the influence of individual deformation and recrystallisation mechanisms on the microstructure and texture evolution during deformation of magnesium sheet alloys. The in-situ measurement method at the synchrotron beam allows a time-resolved description of the defect and texture development in a constant sample volume during well-defined thermo-mechanical treatments, which offers an excellent experimental basis for the analysis of the mechanisms of the microstructure changes. Concurrent to this approach micro-mechanisms are examined on a grain scale (micrometre or nanometre scale) using electron microscopy, e.g. SEM-EBSD and TEM. The influence of alloying elements, particularly rare earth elements or similar-acting elements as well as the effect of a thermo-mechanical treatment on the activation of deformation mechanisms and recrystallisation is examined in a combined approach. Understanding single mechanisms and their competitive contribution on the resulting microstructure, texture development and mechanical properties allows the relative significance of such mechanisms to be derived. Furthermore, the results allow a metal physical based control of the texture development during rolling of magnesium sheets.

• DFG Programme: Research Grants