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  Precipitation hardening effects on extension twinning in magnesium alloys

Fan, H., Zhu, Y., El-Awady, J. A., & Raabe, D. (2018). Precipitation hardening effects on extension twinning in magnesium alloys. International Journal of Plasticity, 106, 186-202. doi:10.1016/j.ijplas.2018.03.008.

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Fan, Haidong1, 2, Author           
Zhu, Yaxin3, Author           
El-Awady, Jaafar A.4, Author           
Raabe, Dierk2, Author           
1Key Laboratory of Energy Engineering Safety and Disaster Mechanics (Ministry of Education), Department of Mechanics, Sichuan University, Chengdu, China, persistent22              
2Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society, ou_1863381              
3Department of Mechanics, Huazhong University of Science and Technology, Wuhan, China, persistent22              
4Department of Mechanical Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, MD, USA, persistent22              


Free keywords: Age hardening; Hardening; Hardness; Magnesium printing plates; Mean field theory; Molecular dynamics; Plasticity; Precipitates; Precipitation (chemical); Stacking faults, Basal dislocations; Hardening effects; Mean field modeling; Metallic material; Molecular dynamics simulations; Plastic relaxation; Shape effect; Strength and ductilities, Magnesium alloys
 Abstract: Precipitation is an efficient method to strengthen metallic materials. While precipitation hardening effects on dislocation slip have been studied extensively in the past, the influence of precipitates on twinning mediated plasticity and the development of corresponding hardening models that account for twin-precipitate interactions have received less attention. Here, the interaction of 10-12 extension twin boundaries (TBs) in pure magnesium with precipitates of plate-, sphere- and rod-like shapes is studied using molecular dynamics (MD) simulations. We find that TBs that engulf precipitates are absorbed by the precipitate-matrix interfaces, and the precipitates are neither twinned nor sheared but deform elastically leading to their rotation. TBs can pass small precipitates (length? 20 nm) and remain intact. In contrast when TBs are interacting with large precipitates (length? 50 nm), basal dislocations or stacking faults nucleate from the interfaces, causing local plastic relaxation. The stress field around a plate-like precipitate as calculated in the MD simulations suggests that a strong back-stress is imposed on the TBs. We then coarse grain these mechanisms into an analytical mean field model of precipitation hardening on twinning in magnesium alloys, which is based on the energy conservation during the TB-precipitate interaction. The model is in good agreement with the current MD simulations and published experimental observations. The hardening model shows that spherical precipitates have the strongest hardening effect on twinning, basal and prismatic plate-like precipitates have a medium effect while rod-like precipitates exert the weakest influence. We also find that most types of precipitates show a stronger hardening effect on twinning mediated plasticity than on basal dislocation slip. Finally, prismatic plate-like precipitates are predicted to have reasonable hardening effects on both twinning and basal slip. These results can help guiding the development of magnesium alloys with enhanced strength and ductility. © 2018 Elsevier Ltd.


Language(s): eng - English
 Dates: 2018-07
 Publication Status: Issued
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1016/j.ijplas.2018.03.008
BibTex Citekey: Fan2018186
 Degree: -



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Title: International Journal of Plasticity
  Abbreviation : Int. J. Plast.
Source Genre: Journal
Publ. Info: New York : Pergamon
Pages: - Volume / Issue: 106 Sequence Number: - Start / End Page: 186 - 202 Identifier: ISSN: 0749-6419
CoNE: https://pure.mpg.de/cone/journals/resource/954925544230