Motivation: Mechanical properties of materials are different when sample dimensions are reduced to nano-scale. Conducting in-situ experiments at that scale is challenging yetnecessary to understand true deformation mechanisms and to develop new materials.

CAREER: Experimental Investigation of Plasticity at Nano-scale Julia R. Greer, California Institute of Technology, DMR 0748267

Key Accomplishments:1. Emergence of strain rate

sensitivity in sub-250nm diameter single Xtalline FIB-less Cu nano-pillars due to surface source nucleation1

2. Uniaxial compression on bi-crystalline Al pillars reveal identical size effect, stochastic signature. TEM analysis reveals no dislocation storage near boundary => dislocation sink2

3. Nano-twinned Cu nano-pillars are brittle for TBs orthogonal to loading direction at D = 100nm and ductile when D = 50nm or TBs are slanted

Deviation from Power-LawSmall Pillars & Slow Strain Rates

Size effect identical to single crystalline pillars

Bi-crystalline Al

NSF-SUPPORTEDUNDERGRADUATE STUDENTS

Luis Miramontes (East LA Com. College)Amy Wat (Cal State LA)

Brian Okoro(Caltech SURF)Jarvis Li (Caltech SURF)

Jennifer Zhu (Caltech SURF)Jeff Han(Caltech SURF)

Liz Deconvelaere (Caltech SURF)

NSF-SUPORTED POST-DOCSDongchan Jang

NSF-SUPPORTED GRADUATE STUDENTS

Andrew Jennings (3rd year)Allison Kunz* (2nd year)Zach Aitken (1st year)

RELEVANT PUBLICATIONS (2010-2011):- J.R. Greer and J. Th. M. de Hosson Prog in Mat Sci (invited review) 56, 654–724 (2011).- A.T. Jennings, et al J Mater Res (invited paper) (2011)- Q. Sun, et al Scripta Mater 65, 473-476 (2011) - C.R. Weinberger, et al J Mech Phys Solids (submitted, 2011)- A.T. Jennings, et al Acta Mater.

doi:10.1016/j.actamat.2011.05.038 (2011). - A. Kunz, et al Acta Mater. 59, 4416–4424 (2011)- N. Friedman, et al (submitted, 2011) - D. Jang et al Nano Lett. 11 (4), 1743-1746 (2011)

HIGH SCHOOL STUDENTSJoanne Lynne, Margarette Aguinaldo

BROAD IMPACT PI is faculty advisor for Society of Women Engineers (SWE) and Women

Mentoring Women

SEMINARS (2010-2011):Harvard, KAIST, UIUC, Brown, UC San Diego, Los Alamos NL, Sandia NL

CONFERENCES (2010-11): MRS, TMS, APS, IIW4 ASME, ECI, Plasticity 2011, SES Several“Micromechanics” and “Nano-materials” workshops

CAREER: Experimental Investigation of Plasticity at Nano-scale Julia R. Greer, California Institute of Technology, DMR 0748267