SUBJECT: Ph.D. Dissertation Defense
BY: Shraddha Vachhani
TIME: Tuesday, January 7, 2014, 1:00 p.m.
PLACE: Love Building, 210
TITLE: Evolution of Stored Energy During Deformation in FCC Metals
COMMITTEE: Dr. Surya Kalidindi, Chair (ME)
Dr. Richard Neu (ME)
Dr. Antonia Antoniou (ME)
Dr. Hamid Garmestani (MSE)
Dr. Roger Doherty (MSE, Drexel University)


Microstructure changes that occur during the deformation and heat treatments involved in wrought processing of metals are of central importance in achieving the desired properties or performance characteristics in the finished products. However, thorough understanding of the evolution of microstructure during thermo-mechanical processing of metallic materials is largely hampered by lack of methods for characterizing reliably their local (anisotropic) properties at the sub-micron length scales. Recently, remarkable advances in nanoindentation data analysis techniques have been made which now make it possible to obtain quantitative information about the local mechanical properties of constituent individual grains in polycrystalline metallic samples. In this work, a novel approach that combines mechanical property information obtained from spherical nanoindentation with the complementary structure information measured locally at the indentation site, using orientation imaging microscopy (OIM), is used to systematically investigate the local structure-property relationships in fcc metals. This work is focused on obtaining insights into the changes in local stored energies of polycrystalline metallic samples as a function of their crystal orientation at increasing deformation levels. Furthermore, using the same approach, the evolution of mechanical properties in the grain boundary regions in these samples is studied in order to better understand the role of such interfaces during deformation and recrystallization processes. The findings provide valuable information regarding development of stored energy gradients in polycrystalline materials during macroscopic deformation.