Enhanced Strengthening Mechanisms in Nanocrystalline Alloys

ChEMS Seminar


Featuring: Dr. Timothy Rupert

Assistant Professor

Mechanical & Aerospace Engineering

UC Irvine


Nanocrystalline materials have attracted a great deal of attention in recent years, largely due to their impressive array of physical properties.  Nanocrystalline mechanical behavior has been of particular interest, as incredible strengths are predicted when grain size is reduced to the nanometer range.  The vast majority of research to this point has focused on quantifying and understanding the grain size-dependence of strength, leading to the discovery of novel grain boundary-dominated physics that begin to control deformation at extremely fine grain sizes.  With the emergence of this detailed understanding of nanocrystalline deformation mechanisms, the opportunity now exists for studies that explore how other structural features affect mechanical properties, in order to identify alternative strengthening mechanisms which are active in nanocrystalline alloys.  The work presented in this talk seeks to extend our current knowledge of nanocrystalline structure-property relationships beyond just grain size, to understand how alloying additions and grain boundary defects alter mechanical response.  Controlled experiments on Ni-W are first used to show that solid solution addition and the relaxation of nonequilibrium grain boundaries can dramatically affect the strength of nanocrystalline metals.  Next, the sliding wear response of nanocrystalline Ni-W is investigated, to show how these secondary strengthening mechanisms influence a more complex mechanical property.  In each case discussed above, the observed behavior can be directly connected to the unique nanocrystalline deformation physics.


Dr. Tim Rupert received his Ph.D. degree in Materials Science and Engineering from the Massachusetts Institute of Technology in 2011, after obtaining a joint B.S./M.S.E. in Mechanical Engineering from Johns Hopkins University in 2007.  His expertise is combining experimental, computational, and characterization techniques to study the mechanical behavior and structural stability of nano-scale materials and structures.  Dr. Rupert's research at UCI will concentrate on uncovering new structure-property relationships in advanced nanomaterials for next-generation structural, electronic, and energy components, as well as increasing the reliability and lifetime of these materials.