Toughening and Crack Healing Mechanisms in Nanotwinned Diamond Composites with Various Polytypes

Yongpan Zeng, Qian Zhang, Yujia Wang, Jiaxi Jiang, Hanzheng Xing, and Xiaoyan Li
Phys. Rev. Lett. 127, 066101 – Published 5 August 2021
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Abstract

As an emerging ceramic material, recently synthesized nanotwinned diamond composites with various polytypes embedded in nanoscale twins exhibit unprecedented fracture toughness without sacrificing hardness. However, the toughening and crack healing mechanisms at the atomic scale and the associated crack propagation process of nanotwinned diamond composites remain mysterious. Here, we perform large-scale atomistic simulations of crack propagation in nanotwinned diamond composites to explore the underlying toughening and crack healing mechanisms in nanotwinned diamond composites. Our simulation results show that nanotwinned diamond composites have a higher fracture energy than single-crystalline and nanotwinned diamonds, which originates from multiple toughening mechanisms, including twin boundary and phase boundary impeding crack propagation, crack deflection and zigzag paths in nanotwins and sinuous paths in polytypes, and the formation of disordered atom clusters. More remarkably, our simulations reproduce more detailed crack propagation processes at the atomic scale, which is inaccessible by experiments. Moreover, our simulations reveal that crack healing occurs due to the rebonding of atoms on fracture surfaces during unloading and that the extent of crack healing is associated with whether the crack surfaces are clean. Our current study provides mechanistic insights into a fundamental understanding of toughening and crack healing mechanisms in nanotwinned diamond composites.

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  • Received 10 February 2021
  • Accepted 1 July 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.066101

© 2021 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Yongpan Zeng, Qian Zhang, Yujia Wang, Jiaxi Jiang, Hanzheng Xing, and Xiaoyan Li*

  • Center for Advanced Mechanics and Materials, Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China

  • *Corresponding author. xiaoyanlithu@tsinghua.edu.cn

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Issue

Vol. 127, Iss. 6 — 6 August 2021

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