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Crack propagation mechanism of γ-TiAl alloy with pre-existing twin boundary

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Abstract

The deformation and failure mechanisms of γ-TiAl alloy with pre-existing crack and twin boundary are investigated by using molecular dynamics simulation. The effects of the crack position on the deformation and failure mechanisms of γ-TiAl specimen are analysed through the snapshots of crack propagation, microstructure of crack tip and stress-strain curves. The simulation results show that the dislocation motion is impeded, the good ductility can be maintained and the strength would be improved simultaneously by the twin boundary. The microstructure evolution of crack tip would change with crack positions. Essentially, the deformation behaviour mainly results from the reaction of dislocation-dislocation, dislocation-twin and twin-twin. Besides, the hierarchical twin is a main plastic deformation mechanism leading to strength of γ-TiAl specimen enhancement with non-compromising ductility and strain hardening. Based on stress-strain curves, it can be concluded that the yield strength varies with crack positions. They are the determinant factors for variation of the yield strength with different crack positions such as dislocation behaviour, stacking fault and hierarchical twin. The ductile-brittle transition associated with the dislocation motion and the decohesion failure of crack tip atom can be observed from the lower boundary crack and the center crack models. The crack propagation caused by the coalescent of the void and the crack tip is the main failure mechanism of γ-TiAl specimen. In addition, the results reveal that the mechanism of crack propagation would be influenced by pre-existing twin boundary which can prevent the crack propagation and improve the fracture toughness.

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Authors and Affiliations

  1. Engineering Research Center of Nonferrous Metallurgy’s New Equipment, Ministry of Education, Lanzhou University of Technology, Lanzhou, 730050, China

    Hui Cao, ZhiYuan Rui, WenKe Chen, RuiCheng Feng & ChangFeng Yan

  2. School of Mechanical and Electronical Engineering, Lanzhou University of Technology, Lanzhou, 730050, China

    Hui Cao, ZhiYuan Rui, WenKe Chen, RuiCheng Feng & ChangFeng Yan

  3. State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou, 730050, China

    Hui Cao, ZhiYuan Rui, WenKe Chen, RuiCheng Feng & ChangFeng Yan

Authors
  1. Hui Cao
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  2. ZhiYuan Rui
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  3. WenKe Chen
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Correspondence to ZhiYuan Rui.

Additional information

This work was supported by the National Natural Science Fundation of China (Grant Nos. 51665030, 51865027), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No. IRT_15R30), and the Doctoral Research Foundation of Lanzhou University of Technology.

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Cao, H., Rui, Z., Chen, W. et al. Crack propagation mechanism of γ-TiAl alloy with pre-existing twin boundary. Sci. China Technol. Sci. 62, 1605–1615 (2019). https://doi.org/10.1007/s11431-017-9307-5

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  • DOI: https://doi.org/10.1007/s11431-017-9307-5

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