In situ atomic-scale observation of twinning-dominated deformation in nanoscale body-centred cubic tungsten

Jiangwei Wang; Zhi Zeng; Christopher R Weinberger; Ze Zhang; Ting Zhu; Scott X Mao

doi:10.1038/nmat4228

In situ atomic-scale observation of twinning-dominated deformation in nanoscale body-centred cubic tungsten

Nat Mater. 2015 Jun;14(6):594-600. doi: 10.1038/nmat4228. Epub 2015 Mar 9.

Authors

Jiangwei Wang¹, Zhi Zeng², Christopher R Weinberger³, Ze Zhang⁴, Ting Zhu⁵, Scott X Mao⁶

Affiliations

¹ Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
² Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
³ 1] Materials Science and Engineering Center, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA [2] Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania 19104, USA.
⁴ Department of Materials Science and Engineering and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China.
⁵ 1] Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA [2] School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
⁶ 1] Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA [2] Department of Materials Science and Engineering and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China.

PMID: 25751073
DOI: 10.1038/nmat4228

Abstract

Twinning is a fundamental deformation mode that competes against dislocation slip in crystalline solids. In metallic nanostructures, plastic deformation requires higher stresses than those needed in their bulk counterparts, resulting in the 'smaller is stronger' phenomenon. Such high stresses are thought to favour twinning over dislocation slip. Deformation twinning has been well documented in face-centred cubic (FCC) nanoscale crystals. However, it remains unexplored in body-centred cubic (BCC) nanoscale crystals. Here, by using in situ high-resolution transmission electron microscopy and atomistic simulations, we show that twinning is the dominant deformation mechanism in nanoscale crystals of BCC tungsten. Such deformation twinning is pseudoelastic, manifested through reversible detwinning during unloading. We find that the competition between twinning and dislocation slip can be mediated by loading orientation, which is attributed to the competing nucleation mechanism of defects in nanoscale BCC crystals. Our work provides direct observations of deformation twinning as well as new insights into the deformation mechanism in BCC nanostructures.