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Dual-phase nanostructuring as a route to high-strength magnesium alloys

Nature volume 545, pages 8083 (04 May 2017) | Download Citation

Abstract

It is not easy to fabricate materials that exhibit their theoretical ‘ideal’ strength. Most methods of producing stronger materials are based on controlling defects to impede the motion of dislocations, but such methods have their limitations. For example, industrial single-phase nanocrystalline alloys1,2 and single-phase metallic glasses3 can be very strong, but they typically soften at relatively low strains (less than two per cent) because of, respectively, the reverse Hall–Petch effect4 and shear-band formation. Here we describe an approach that combines the strengthening benefits of nanocrystallinity with those of amorphization to produce a dual-phase material that exhibits near-ideal strength at room temperature and without sample size effects. Our magnesium-alloy system consists of nanocrystalline cores embedded in amorphous glassy shells, and the strength of the resulting dual-phase material is a near-ideal 3.3 gigapascals—making this the strongest magnesium-alloy thin film yet achieved. We propose a mechanism, supported by constitutive modelling, in which the crystalline phase (consisting of almost-dislocation-free grains of around six nanometres in diameter) blocks the propagation of localized shear bands when under strain; moreover, within any shear bands that do appear, embedded crystalline grains divide and rotate, contributing to hardening and countering the softening effect of the shear band.

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Acknowledgements

This work is supported in part by the Major Program of the National Natural Science Foundation of China (NSFC) grant 51590892 and the Hong Kong Collaborative Research Fund (CRF) Scheme (C4028-14G and CityU9/CRF/13G). We thank Q. Wang for technical discussions and Z. F. Zhou for assistance with magnetron sputtering at the City University of Hong Kong.

Author information

Affiliations

  1. Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong, China

    • Ge Wu
    • , Ka-Cheung Chan
    • , Linli Zhu
    • , Ligang Sun
    •  & Jian Lu
  2. Department of Engineering Mechanics and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou 310027, China

    • Linli Zhu
  3. Centre for Advanced Structural Materials, City University of Hong Kong, Shenzhen Research Institute, 8 Yuexing 1st Road, Shenzhen Hi-Tech Industrial Park, Nanshan District, Shenzhen, China

    • Jian Lu

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Contributions

J.L. designed the project. G.W. and J.L. designed the material and experiments. G.W. conducted the nanoindentation and SEM in situ microcompression experiments and the TEM characterization. K.-C.C. conducted the focused-ion-beam experiments. L.Z. developed the theoretical model. L.S. performed the molecular-dynamics simulation. G.W. and J.L. analysed the data and wrote the paper. All authors contributed to discussion of the results.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Jian Lu.

Reviewer Information Nature thanks X. Li, J.-F. Nie and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Videos

  1. 1.

    In-situ micro-compression movie (4× speed) of the 1300-nm-sized pillar

    In-situ micro-compression movie (4× speed) of the 1300-nm-sized pillar.

  2. 2.

    In-situ micro-compression movie (4× speed) of the 300-nm-sized pillar

    In-situ micro-compression movie (4× speed) of the 300-nm-sized pillar.

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DOI

https://doi.org/10.1038/nature21691

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