Investigation of the role of different grain boundaries in plasticity and microstructure formation during dynamic recrystallization of Mg

点击翻译按钮获取中文摘要

The aim of the proposed research project is to systematically examine the impact of different grain boundaries and grain boundary triple lines on the plasticity and dynamic recrystallization of magnesium. A particular focus will be put on the mechanisms of deformation and microstructure development in the presence of specific grain boundaries, on the influence of the grain boundary geometry, topology and thermodynamics of the grain boundary network. For investigations the bi-, tri- and oligocrystalline samples of pure Mg and Mg alloys will be used, which will be specially grown utilizing newly developed technique in the recently designed high-frequency induction furnace. Besides deformation by plane strain compression also in-situ experiments utilizing the special testing unit integrated in the scanning electron microscope will be performed. Furthermore, the mechanically induced shear-coupled motion of geometrically different grain boundaries in bicrystals will be measured. Finally, the nanoindentation technique will be applied in order to study the plasticity of magnesium in the close vicinity of various grain boundaries. The new knowledge gained from the proposed investigations on the mechanisms of the microstructure evolution during deformation and dynamic recrystallization will make a significant contribution towards an understanding the role of grain boundaries during deformation of polycrystalline magnesium and magnesium alloys.The proposed research program consists of five work packages. In the first package the specially grown bi-, tri- and oligocrystals will be deformed by plane strain compression and subsequently investigated in order to get a comprehensive picture of the impact of various grain boundaries on plasticity and dynamic recrystallization of magnesium. The second package comprises in-situ investigations of mechanical twinning initiated on grain boundaries, the formation of new grains at the early stages of recrystallization and the interaction between moving dislocations and grain/twin boundaries. In the third project work package the investigations on the deformation and recrystallization behavior will be extended to bicrystals of Mg-Gd and Mg-Zn alloys. Also, in the fourth work package stress driven migration of various grain boundaries, associated with a shear/plastic deformation, will be measured and comprehensively analyzed. In the fifth work package of the program the deformation behavior of magnesium in the vicinity of grain boundaries will be investigated in dependence of grain boundary character by applying the technique of nanoindentation.