Papers by Author: Names Chandra

Abstract: In this paper we address the controversial issue of nucleation of cavities in Al 5083 alloys and their subsequent growth to coalescence and failure. We focus on the origin and growth of cavities not only during the primary processing of Al 5083 in sheet forms, but also during the manufacture of these sheets into SPF (superplastic forming) components. Experimental observations of pre-existing cavities in this alloy are made using optical and electron microscopy. The role of sheet rolling direction, and the state of stress during superplastic deformation on the cavity formation and coalescence are also discussed. The effect of the state of stress (uniaxial, plane strain, balanced biaxial, and tri-axial) on the growth characteristics of cavitation is also examined. It is found that the uniaxial model based cavitation cannot directly be extended to predict the behavior of more complex stress states, unless great care is taken to identify the right strain measure for the mapping process.

Abstract: The microstructure of friction stir processed AA5052 sheets is investigated using Scanning Electron Microscopy (SEM) and Orientation Imaging Microscopy. The correlation between the generated forces during processing and the microstructure is evaluated. Observations indicate that the finest microstructure are achieved when the plunging forces are at minimum.