Lead P.I. - Dr. Jason R. Trelewicz

Crystalline solids with strengths near the theoretical limit have been inaccessible to date due to plasticity being controlled by the onset of dislocation motion.  The pursuit of high strength materials thus has largely focused on incorporating obstacles to long-range dislocation motion and has led to common strengthening routes for materials: work hardening, solid solution strengthening, precipitation strengthening, and grain size strengthening.  In contrast, nanocrystalline materials offer a unique opportunity to push the limits of dislocation propagation near the stresses needed for lattice instability since long-range dislocation motion is already restricted by the extremely small grain size.  The guiding hypothesis is that dopants stabilize the grain boundaries against local plasticity, which in turn suppresses dislocation nucleation with propagation inhibited through synergistic doping of the lattice, thereby providing a mechanistic pathway toward achieving theoretical strength.  The figure above illustrates an overview of (a-d) experimental characterization and thermal staiblity of nanocrystalline Al-7 at.% Mg and (e-f) atomistic simulations of dislocation dyanmics and strain accomodation.  A particuarly unique finding with implications for sintering is the presence of Mg-rich nanoclusters.  In a broad sense, this research will define new strengthening paradigms in nanoengineered metallic materials and establish the mechanistic underpinnings of their deformation behavior.