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Journal of Nanomaterials
Volume 2013, Article ID 934986, 5 pages
http://dx.doi.org/10.1155/2013/934986
Research Article

Effects of Free Surface and Heterogeneous Residual Internal Stress on Stress-Driven Grain Growth in Nanocrystalline Metals

1State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, China
2State-Key Laboratory for Mechanical Behavior of Material, Xi’an Jiaotong University, Xi’an 710049, China
3INM-Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrucken, Germany

Received 18 June 2013; Revised 24 August 2013; Accepted 28 August 2013

Academic Editor: Tianxi Liu

Copyright © 2013 F. Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

By reevaluating the experimental study of Zhang et al. (2005), here we demonstrate that the extent of grain growth, previously proposed to be solely driven by external stress, may have been significantly overestimated. A new physical mechanism, termed as free surface assisted stress-driven grain growth (or self-mechanical annealing), is proposed and discussed in detail. Representing the cooperative effect of free surface and heterogeneous residual internal stress, the proposed mechanism is considered more favorable than the traditional pure stress-driven mechanism for interpreting the abnormal grain growth widely observed in deforming nanocrystalline metals at room temperature.