Acta Materialia, Volume 60, Issue 3, February 2012, Pages 1368-1377
Zhang-Jie Wang, Zhi-Wei Shan, Ju Li, Jun Sun, Evan Ma
Center for Advancing Materials Performance from the Nanoscale (CAMP-Nano) & Hysitron Applied Research Center in China (HARCC), State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China
Department of Nuclear Science and Engineering and Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
Abstract
Pristine single crystalline gold particles with sizes ranging from 300 to 700 nm have been fabricated through high-temperature (1150 °C) liquid de-wetting of gold thin films atop a specially designed SiO2/Si substrate for in situ transmission electron microscopy testing. Quantitative compression tests showed that these particles display cataclysmic structural collapse immediately following elastic loading to very high stresses (over 1 GPa), resulting in a nearly pristine postmortem microstructure despite the large plastic deformation experienced by the particle. This distinct class of dislocation plasticity behavior is attributed to the very high degree of structural perfection of the initial sample, resulting from high-temperature formation or annealing around the melting point. Temporally correlated dislocation nucleation from the contact interface together with the inability to form stable junctions inside is proposed to explain the pristine-to-pristine structural collapse. Upon further compression, once the contact diameter d increases to above a critical value (∼250 nm), continuous plastic deformation begins to set in under relatively low flow stress with the postmortem microstructure containing a high density of tangled dislocations, suggesting that a critical dislocation tangling volume under multiple slip is needed for the onset of dislocation storage (robust dislocation jamming) and more conventional plasticity.
