Cooperative Grain Boundary Sliding and Heterogeneities of Grain Boundary Character Distribution in Superplastic Materials

0109535 Garmastani该项目旨在使用最新的数字成像和原位显微镜技术更好地了解不同铝合金结构超塑性变形的基本机制。它已被确定为晶界滑动微晶超塑性操作不均匀和合作的方式。协作晶界滑动的非均匀性的本质仍然不清楚。对这种重要变形模式的起源的基本理解对于改进超塑性理论模型以及设计具有改进的超塑性性能的先进材料可以是富有成效的。本研究的主要目标是：（1）确定晶界协同滑动与晶界失向的关系三种细晶铝合金的介观织构（2）研究了这些合金中晶界滑移的拓扑模式;（3）研究晶界协同滑动的调节机制。为了达到这些目标，两种不同的微观表征技术结合在一起：扫描电子显微镜中的定向成像显微镜（OIM）和扫描探针显微镜的纳米划痕。这项工作是基于原位微拉伸阶段的能力，将用于结合真实的时间OIM分析，以提供重要的信息的性质晶界滑动。这项研究的资金提供了第一手接触研究的前沿科学和技术的少数民族学生在FAMU-FSU工程学院。这项研究发展了对超塑性机制的新理解，超越了目前的技术水平。研究结果适用于通过近净成形来节省金属制造成本。该研究将为少数民族教育和研究做出重大贡献。

0109535GarmastaniThis project is aimed at greater understanding of fundamental mechanisms of structural superplastic deformation in different aluminum alloys using the most current digital imaging and insitu microscopy techniques. It has been established that grain boundary sliding during micrograin superplasticity operates heterogeneously and in a cooperative manner. The nature of heterogeneity of cooperative grain boundary sliding remains unclear. Fundamental understanding of the origin of this important deformation mode can be fruitful for the improvement of theoretical models of superplasticity as well as for the design of advanced materials with improved superplastic properties. The main goals of this study are: (1) to determine the relationship between cooperative grain boundary sliding and grain boundary disorientation (mesotexture) in three fine-grained aluminum alloys (AA7475, AA5083 and D19) that manifest different micro-mechanical behavior; (2) to study topological modes of grain boundary sliding in these alloys; (3) to investigate accommodation mechanisms for cooperative grain boundary sliding. To reach these goals two different micro-characterization techniques are combined together: Orientation Imaging Microscopy (OIM) in Scanning Electron Microscope and Nanoscratching with Scanning Probe Microscope. The work is based on insitu micro-tensile stage capability that will be used in conjunction with real time OIM analysis to provide important information on the nature of the grain boundary sliding. The funding for this research provides a first hand exposure to research in forefront of science and technology to minority students at FAMU-FSU College of Engineering. %%%This research develops new understanding of the mechanisms involved with superplasticity beyond the present state of the art. The results are applicable for cost savings for metal fabrication through near net shaping. The research will make significant contributions to minority education and research.***