期刊
ACTA MATERIALIA
卷 149, 期 -, 页码 407-415出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2018.02.062
关键词
TWIP steel; Nanotwin; Ballistic impact; High-strain-rate deformation
资金
- Research Grants Council of Hong Kong [HKU719712E, HKU712713E, 17203014]
- University Grants Committee of the Hong Kong Special Administrative Region, China [SEG_HKbu06]
- Department of Physics, the Chinese University of Hong Kong
Nanotwinned metals are promising structural materials for resisting impact due to their excellent combination of strength and ductility. In this study, the microstructural evolution of a nanotwinned steel under extremely high-strain-rate ballistic impact was systematically investigated by nanoindentation as well as detailed electron microscopy characterization. It is found that the nanotwin structure remains similar after ballistic impact, while secondary twinning activates in a limited portion of grains. In contrast, dislocation gliding is the main plasticity mechanism in the nanotwinned steel during ballistic impact, which leads to substantial increase of hardness in the severely-deformed region close to the fracture surface. Dislocation multiplication is promoted during ballistic impact due to the phonon drag effect, resulting in a hardness increment that exceeds the maximum value achieved in quasi-static tension. In addition, recrystallization occurs in the nanotwinned steel during ballistic impact due to the significant temperature increase when the hot bullet contacted and transferred sufficient heat to the nanotwinned steel. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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