Microscale Mechanical Characterization of Materials for Extreme Environments
Sezer Özerinç, University of Illinois at Urbana-Champaign
Date: Friday, December 19, 2014
Place: EA 409
Nanostructured metals are promising materials for applications that require outstanding strength and stability at extreme environments. We combine mechanical and microstructural characterization techniques to obtain a better understanding of deformation mechanisms in these materials. Our recent nanoindentation hardness measurements on metal alloys have demonstrated that grain boundary doping enhances the strength of nanocrystalline copper far beyond that predicted by classical Hall- Petch strengthening. Grain boundary composition measurements and MD simulations show that decreasing grain boundary energy is the key to reaching theoretical strength in nanocrystalline metals. Micropillar compression is a more recent and effective technique for probing yield strength at the nanoscale. We have used this technique to characterize the interface shear strength of Cu-Nb multilayers, a promising nanomaterial of excellent strength and thermal stability. Measurements indicate that Cu-Nb shear strength increases with chemical mixing at the interface, which has important implications for proposed use of multilayered materials in extreme environments. The micropillar compression technique has also enabled a new approach to in situ characterization of irradiation-induced creep, a deformation mechanism of critical importance for nuclear applications. We have developed an in situ measurement apparatus for compression testing of micron-sized cylindrical specimens under MeV heavy ion bombardment. We measured irradiation-induced creep in four different amorphous materials and clarified the significance of different creep mechanisms in these materials. The developed apparatus provides a new and effective method of accelerated characterization of promising materials for future nuclear power plants.
Sezer Özerinç is a Ph.D. candidate in Mechanical Science and Engineering in University of Illinois at Urbana-Champaign, under the supervision of Prof. William P. King. He received his B.S. degree in Mechanical Engineering from Middle East Technical University in 2008, ranking first in his class. He received his M.S. degree also from METU in 2010 under the co-supervision of Prof. Sadık Kakaç and Assoc. Prof. Almıla G. Yazıcıoğlu. His M.S. thesis focused on the numerical analysis of convective heat transfer in nanofluids. His Ph.D. work includes mechanical and microstructural characterization of nanostructured materials and development of an in situ mechanical testing technique for nuclear applications.