M.S. Thesis Presentation by Jean-Baptiste Bergugnat
Friday, October 11, 2002

(Dr. David McDowell, advisor)

"Strain and Lattice Rotation Fields of Deformed Polycrystals"

Abstract

High-resolution experimental characterization of material stretch and rotation fields in relatively fine-grained polycrystals has been limited, inhibiting direct comparison with predictions of crystal plasticity theory. Polycrystals plasticity models based upon the work of Taylor (1938) are founded upon the assumptions that the fundamental unit of deformation is at the scale of the grain and that the displacement field is homogeneous amongst all grains in the aggregate. This has shown to offer a reasonable first order assumption, but it is widely known that the strain field within individual grains is non uniform.

In this thesis, material stretch and rotation field of deformed polycrystals, in this case OFHC copper with and without Sb additions, are measured using a photolithographic grid deposition technique developed by Schroeter (2001) at the subgrain resolution scale, and Electron Back Scattering Diffraction (EBSD) is used to measure lattice disorientation fields within grains. Out of plane displacements are also measured. These studies are conducted for both polycrystalline OFHC Cu and Cu with 0.2-wt% antimony (Sb), a segregant that induces embrittlement at the grain boundaries that favors intergranular fracture.