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

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

0109535 Garmastani This 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. ***