Continuous Recrystallization and Grain Boundaries in a Superplastic Aluminum Alloy
Superplasticity refers to exceptional tensile ductility for certain polycrystalline materials when they are deformed under appropriate temperature and strain rate conditions. Utilization of superplastic forming has experienced steady growth in recent years due to component weight savings as well as improved performance and reliability for engineering systems incorporating this technology (Grimes, 1988). However, despite such benefits the range of available alloy compositions suitable for use in superplastic forming of components has remained restricted. Improvements in the forming characteristics and superplastic response for a wider range of engineering aluminum alloys than is currently the case would enable great expansion of the utilization of this technology. The micro structural prerequisites that must be met to enable superplasticity are now well established. They include highly refined grains, smaller than 10 μm in size, and grain boundaries capable of sliding while resisting tensile separation (Sherby and Ruano, 1982; Langdon, 1982). The need for a fine grain size reflects the independent contributions of grain boundary sliding (GBS) and slip creep during elevated temperature deformation (Sherby and Ruano, 1982; Langdon, 1982; Sherby and Wadsworth, 1984; Ruano and Sherby, 1988).
KeywordsOrientation Distribution Function Grain Boundary Slide Continuous Recrystallization Disorientation Angle Cellular Dislocation Structure
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