Materials World Network: Characterization and Modeling of the Interplay between Grain Boundaries and Heterogeneous Plasticity in Titanium

晶界强化效应是现代结构材料发展的关键组成部分之一，是超细晶和纳米结构材料以及晶界工程产生有益效应的原因。然而，对晶界通常有益影响的确切性质尚未理解到允许理论指导的微观结构优化和加速合金发展的水平。在这项研究中，基于密歇根州立大学（MSU）和德国d<s:1> sseldorf的马克斯普朗克研究所（MPIE）的合作，研究人员结合，改进和应用最近开发的方法，使用基于显微镜和锥形压痕测试的技术来检查和量化晶界的微观力学行为。结合使用电子背散射电子图谱、原子力显微镜、3-D x射线表征和聚焦离子束/电子成像方法，提供了活化滑移行为的量化测量。这些方法用于评估由锥形压痕引起的变形，以将详细的压痕地形与单晶的塑性各向异性联系起来。与传统的单晶和双晶实验相比，该方法具有效率优势。最初,?单晶?表征将使用晶粒内部的压痕进行，并且由于在晶体塑性有限元分析中使用基于位错密度的本构模型来开发建模保真度，晶界附近和晶界上的压痕将用于评估滑移的晶界透射率和机械孪晶行为。根据观察到的透射率行为，将晶界透射率模型实现到本构模型中。所实现的方法与最先进的表征和模拟方法相结合，可以定量地了解钛多晶中晶界和非均质塑性之间的相互作用。在表征（MSU）和模拟（MPIE）互补的技能是可用的，以达到既定目标。两个实验室之间的广泛交流主要在夏季进行，以便整合实验和分析结果。

The strengthening effect of grain boundaries is one of the key components in the development of modern structural materials which is responsible for beneficial effects arising from ultra fine grained and nanostructured materials, and grain boundary engineering. The precise nature of the often beneficial effects of grain boundaries, however, has not been understood to a level which would allow for theory-guided optimization of microstructures and accelerated alloy development. In this research, based on collaboration between Michigan State University (MSU) and the Max Planck Institut für Eisenforschung (MPIE) in Düsseldorf, Germany, the investigators combine, improve, and apply recently developed approaches to examine and quantify the micromechanical behavior of grain boundaries using techniques based upon microscopy and conical indentation tests. Combined use of electron backscattered electron pattern mapping, atomic force microscopy, 3-D x-ray characterization, and focused ion beam/electron imaging methods provide quantified measures of activated slip behavior. These methods are used to assess deformation caused by conical indentation to relate detailed indentation topographies to the plastic anisotropy of single crystals. The methods provide an efficiency advantage over traditional single and bi-crystal experiments. Initially, ?single crystal? characterization will occur using indents in grain interiors, and as modeling fidelity is developed using dislocation density based constitutive models implemented in crystal plasticity finite element analyses, indentations near and on grain boundaries will be used to assess the grain boundary transmissivity of slip and mechanical twinning behavior. From observed transmissivity behavior, models for grain boundary transmissivity will be implemented into the constitutive models.The implemented approach, combined with state of the art characterization and simulation methods, can lead to a quantitative understanding of the interplay between grain boundaries and heterogeneous plasticity in titanium polycrystals. Complementary skills in characterization (MSU) and simulation (MPIE) are available to reach the stated goals. Extensive exchanges between the two laboratories occur principally during summers in order to integrate experimental and analytical outcomes.