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Published April 2005 | public
Journal Article

Size dependence of mechanical properties of gold at the micron scale in the absence of strain gradients

Abstract

Classical laws of mechanics hold that mechanical properties are independent of sample size; however, results of experiments and molecular dynamics simulations indicate that crystals exhibit strong size effects at the sub-micron scale. In experimental studies, the size effect can be explained by strain gradients. Atomistic simulations suggest that the yield strength depends on the size even without strain gradients and scales with the sample size through a power relationship. We address these different approaches to the size dependence of mechanical properties. Results of uniaxial compression experiments on gold at the sub-micron scale, without stress/strain gradients, are presented here. Freestanding Au cylinders are created by two unique fabrication processes and subsequently compressed in the Nanoindenter with a flat punch. Compressive stress, strain, and stiffness of the pillars are determined. Test results indicate a significant flow stress increase, up to several GPa. These high strengths appear to be controlled by dislocation starvation, unique to small crystals.

Additional Information

© 2005 Acta Materialia Inc. Published by Elsevier Ltd. Received 13 November 2004; received in revised form 6 December 2004; accepted 17 December 2004. Available online 26 January 2005. The authors thank R. True of Nanoplex and Dr. E. Perozziello of Stanford Nanofabrication Facility for their tremendous help with the microfabrication techniques. They also acknowledge Kermit Parks of MTS for his indispensable help with the Nanoindenter, and Feng Gang for his help with Testworks. The valuable discussions and support of Dr. Michael Uchic of the AFRL Materials Lab in connection with this work is greatly appreciated. The authors also gratefully acknowledge financial support of this project through grants provided by an NSF-NIRT grant (CMS-0103257) and the Department of Energy (DE-FG03-89ER45387).

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023