Anti-twinning in nanoscale tungsten

Jiangwei Wang; Zhi Zeng; Minru Wen; Qiannan Wang; Dengke Chen; Yin Zhang; Peng Wang; Hongtao Wang; Ze Zhang; Scott X Mao; Ting Zhu

doi:10.1126/sciadv.aay2792

Anti-twinning in nanoscale tungsten

Sci Adv. 2020 Jun 3;6(23):eaay2792. doi: 10.1126/sciadv.aay2792. eCollection 2020 Jun.

Authors

Jiangwei Wang¹, Zhi Zeng², Minru Wen^{2

3}, Qiannan Wang¹, Dengke Chen², Yin Zhang², Peng Wang^{4

5}, Hongtao Wang⁴, Ze Zhang¹, Scott X Mao⁶, Ting Zhu²

Affiliations

¹ Center of Electron Microscopy and State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
² Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
³ School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China.
⁴ Center for X-Mechanics, Zhejiang University, Hangzhou 310027, China.
⁵ Materials Genome Institute, Shanghai University, Shanghai 200444, China.
⁶ Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261, USA.

Abstract

Nanomaterials often surprise us with unexpected phenomena. Here, we report a discovery of the anti-twinning deformation, previously thought impossible, in nanoscale body-centered cubic (BCC) tungsten crystals. By conducting in situ transmission electron microscopy nanomechanical testing, we observed the nucleation and growth of anti-twins in tungsten nanowires with diameters less than about 20 nm. During anti-twinning, a shear displacement of 1/3〈111〉 occurs on every successive {112} plane, in contrast to an opposite shear displacement of $1 / 6 〈 \bar{1} \bar{1} \bar{1} 〉$ by ordinary twinning. This asymmetry in the atomic-scale shear pathway leads to a much higher resistance to anti-twinning than ordinary twinning. However, anti-twinning can become active in nanosized BCC crystals under ultrahigh stresses, due to the limited number of plastic shear carriers in small crystal volumes. Our finding of the anti-twinning phenomenon has implications for harnessing unconventional deformation mechanisms to achieve high mechanical preformation by nanomaterials.

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