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Sci Rep. 2018 Jan 25;8(1):1614. doi: 10.1038/s41598-018-20150-5.

Structural effect of two-dimensional BNNS on grain growth suppressing behaviors in Al-matrix nanocomposites.

Author information

1
School of Advanced Materials Engineering, Kookmin University, Seoul, 02707, Republic of Korea.
2
Nuclear Materials Safety Research Division, Korea Atomic Energy Research Institute, Daejeon, 34057, Republic of Korea.
3
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, Jeonbuk, 55324, Republic of Korea.
4
Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, TX, 75080, USA.
5
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, Jeonbuk, 55324, Republic of Korea. junyeon.hwang@kist.re.kr.
6
School of Advanced Materials Engineering, Kookmin University, Seoul, 02707, Republic of Korea. hyunjoo@kookmin.ac.kr.

Abstract

While nanocrystalline (NC) metals exhibit superior strength to conventional microcrystalline metals, their thermal instability has hampered their application at high temperatures. Herein, two-dimensional (2D) boron nitride nanosheets (BNNS) are proposed as reinforcement to enhance the strength as well as the thermal stability of NC Al. The strength of pure Al was increased from 80 to 468 MPa by refining its grains from ~600 to ~40 nm, and it was further enhanced to 685 MPa by incorporating 2 vol% of BNNS. Moreover, the small amount of BNNS was found to effectively suppress grain growth of NC Al at 580 °C (~0.9 Tm, where Tm is the melting point of Al), which prevented a strength drop at high temperature. Finally, the Zener pinning model in conjunction with phase-field simulations was utilized to qualitatively analyze the effect of the BNNS on the grain boundary pinning as a function of volume, shape, and orientation of the reinforcement. The model demonstrated that the pinning force of 2D reinforcements is much higher than that of spherical particles. Hence, 2D BNNS offer the possibility of developing Al-matrix nanocomposites for high-temperature structural applications.

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