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

轧制过程中微观结构和织构的形成决定了镁板的性能及其轻量化应用的技术潜力。弱化织构或改变主要织构成分以及晶粒细化，可显著提高板材的成形性。然而，这样的织构导致力学各向异性增强。目前，人们讨论了许多不同的机制对微观结构和织构发展的影响。虽然分析揭示了在轧制过程中不同变形机制激活的改变以及对再结晶行为的影响，但在三元镁合金中添加稀土元素或钙对这些机制的影响以及对组织和织构发展的影响尚不清楚。本项目的目的是利用同步辐射进行原位硬x射线衍射实验，以得出关于镁合金变形过程中个别变形和再结晶机制对组织和织构演变的影响的直接结论。同步加速器束的原位测量方法可以在确定的热机械处理过程中，以恒定的样品体积对缺陷和织构发展进行时间分辨描述，这为分析微观结构变化的机制提供了良好的实验基础。与此同时，在晶粒尺度（微米或纳米尺度）上使用电子显微镜（例如SEM-EBSD和TEM）检查微观机制。合金元素，特别是稀土元素或类似作用元素的影响，以及热处理对变形机制和再结晶激活的影响，将以综合的方法进行检验。了解单一机制及其对微观结构、织构发展和力学性能的竞争性贡献，可以推导出这些机制的相对重要性。此外，该结果允许基于金属物理控制的织构发展过程中的镁板轧制。

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.