Key Accomplishments:

1. CAREER: Experimental Investigation of Plasticity at Nano-scale Julia R. Greer, California Institute of Technology, DMR 0748267 Motivation: Mechanical properties of materials are different when sample dimensions are reduced to nano-scale. Conducting in-situ experiments at that scale is challenging yet necessary to understand true deformation mechanisms and to develop new materials. • Key Accomplishments: • ALD-assivated Cu nano-pillars: exhibit significant hardening, Bauschinger effect; stochastic behavior remains (A. Jennings, S.-W. Lee, Z. Aitken)1 • Intermittent Plasticity of Single Crystalline Nano-Pillars: Scaling-collapse and scaling-function extracted from compression experiments show that nano-plasticity reflects tunedcriticality as opposed to self-organized criticality (SOC). Power-law exponents and scaling-function agree with mean-field theory (MFT) predictions(A. Jennings) • Nanocrystalline Pt: Developed a FIB-less nano-fabrication methodology to create 12nm-grained nc-Pt nano-pillars. Compressive strengths were found to not deviate significantly from bulk even at smallest pillar diameters, ~8 grains across. Sample size independent regime was identified and shown to depend on both grain size and the ratio of external sample size to grain size. (X. W. Gu)

2. CAREER: Experimental Investigation of Plasticity at Nano-scale Julia R. Greer, California Institute of Technology, DMR 0748267 BROAD IMPACT PI is faculty advisor for Society of Women Engineers (SWE) and Women Mentoring Women (WMW) HIGH SCHOOL STUDENTS Bill Guo (Arcadia HS) Madeline Watkins (Mayfield HS) Annie Wu (Los Osos HS) NSF-SUPPORTED UNDERGRADUATE STUDENTS Colleen Loynachan (MIT SURF) Jacqueline Masehi-Lano (Caltech SURF) Matt Wraith (UIUC SURF) • RELEVANT PUBLICATIONS (2011-2012): • A. T. Jennings, et al “Higher Compressive Strengths and Bauschinger Effect in Conformally-Passivated Copper Nanopillars”Acta Mater. 60 (8), (2012) • N. Friedman, et al “Statistics of dislocation slip-avalanches in nano-sized single crystals show tuned critical behavior predicted by a simple mean field model.”Phys Rev Lett (in press, 2012) • A. Jerusalem, et al “Continuum modeling of dislocation starvation and subsequent nucleation in nano-pillar compression.”Scripta Mater. 66 (2), (2012) • C.R. Weinberger, et al “Atomistic simulations and continuum modeling of dislocation nucleation and strength in gold nanowires”J Mech Phys Solids60, 84-103 (2012) NSF-SUPPORTED GRADUATE STUDENTS Z. Aitken (2nf year) X. Wendy Gu (partial) L. Meza (partial) SEMINARS (2011-2012): Harvard, U Tennessee, Ecole Polytechnique, RPI, U Tennessee, IMDEA, UIUC, Northwestern CONFERENCES (2011-12): MRS, TMS, ASME, ECI, Plasticity 2012, SES, Gordon, NANO2012, MMM, ISMEN, and Several“Micromechanics” and “Nano-materials” workshops