Nanocrystalline Alloys: Enhanced Strengthening Mechanisms and Mechanically-Driven Structural Evolution by Timothy J. Rupert M.S.E., Mechanical Engineering Johns Hopkins University, 2007 B.S., Mechanical Engineering Johns Hopkins University, 2007 Submitted to the Department of Materials Science and Engineering in Partial Fulfillment of the Requirement for the Degree of Doctor of Philosophy in Materials Science and Engineering at the Massachusetts Institute of Technology June 2011 © 2011 Massachusetts Institute of Technology. All rights reserved. Signature of Author: Department of Materials Science and Engineering April 21, 2011 Certified by: Christopher A. Schuh Danae and Vasilios Salapatas Professor of Metallurgy Thesis Supervisor Accepted by: Christopher A. Schuh Danae and Vasilios Salapatas Professor of Metallurgy Chair, Departmental Committee for Graduate Students