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Effects of ultrafine nanograins on the fracture toughness of nanocrystalline materials

Published online by Cambridge University Press:  18 July 2011

Yingguang Liu
Affiliation:
Department of Mechanical Engineering, Nanjing University of Technology, Nanjing 210009, Jiangsu, People’s Republic of China
Jianqiu Zhou*
Affiliation:
Department of Mechanical Engineering, Nanjing University of Technology, Nanjing 210009, Jiangsu, People’s Republic of China; and Department of Mechanical Engineering, Wuhan Institute of Technology, Wuhan 430070, Hubei, People’s Republic of China
Tongde Shen
Affiliation:
High-Tech Research Institute & State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, Nanjing 210009, Jiangsu, People’s Republic of China
David Hui
Affiliation:
Department of Mechanical Engineering, University of New Orleans, New Orleans, Louisiana 70148
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

For evaluating the effects of ultrafine nanograins (UFNGs) on the fracture toughness of conventional nanocrystalline (nc) materials, we developed a composite model composed of UFNGs (with a grain size d between 2 and 4 nm) evenly distributed in the conventional nc matrix (20 nm ≤ d ≤ 100 nm). The UFNGs could be treated as a part of triple junctions, denoted as super triple junctions. In the framework of our model, stress concentration near crack tip initiates intergrain sliding that leads to the generation of edge dislocations at super triple junctions. The dependence of critical crack intensity factors on grain size was calculated. It was demonstrated that the existence of the UFNGs approximately doubles the critical crack intensity factors.

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Articles
Copyright
Copyright © Materials Research Society 2011

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