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Materials 2015, 8(8), 5250-5264; doi:10.3390/ma8085250

Dislocation-Governed Plastic Deformation and Fracture Toughness of Nanotwinned Magnesium

Institute of Engineering Mechanics, Beijing Jiaotong University, Beijing 100044, China
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Author to whom correspondence should be addressed.
Academic Editor: Daolun Chen
Received: 15 May 2015 / Revised: 26 July 2015 / Accepted: 4 August 2015 / Published: 13 August 2015
(This article belongs to the Section Structure Analysis and Characterization)
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Abstract

In this work, the plastic deformation mechanisms responsible for mechanical properties and fracture toughness in nanotwinned (NT) magnesium is studied by molecular dynamics (MD) simulation. The influence of twin boundary (TBs) spacing and crack position on deformation behaviors are investigated. The microstructure evolution at the crack tip are not exactly the same for the left edge crack (LEC) and the right edge crack (REC) models according to calculations of the energy release rate for dislocation nucleation at the crack tip. The LEC growth initiates in a ductile pattern and then turns into a brittle cleavage. In the REC model, the atomic decohesion occurs at the crack tip to create a new free surface which directly induces a brittle cleavage. A ductile to brittle transition is observed which mainly depends on the competition between dislocation motion and crack growth. This competition mechanism is found to be correlated with the TB spacing. The critical values are 10 nm and 13.5 nm for this transition in LEC and REC models, respectively. Essentially, the dislocation densities affected by the TB spacing play a crucial role in the ductile to brittle transition. View Full-Text
Keywords: nanotwinned magnesium; molecular dynamics; twin boundaries; plastic deformation; fracture toughness nanotwinned magnesium; molecular dynamics; twin boundaries; plastic deformation; fracture toughness
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. (CC BY 4.0).

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MDPI and ACS Style

Zhou, L.; Guo, Y.-F. Dislocation-Governed Plastic Deformation and Fracture Toughness of Nanotwinned Magnesium. Materials 2015, 8, 5250-5264.

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