Structural Effect of Two-Dimensional BNNS on Grain Growth Suppressing Behaviors in Al-Matrix Nanocomposites


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 ⁰C (similar to 0.9 T_m, where T_m 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.


Includes supplementary material


Nanotubes, Nanotubes--Mechanical-properties, High temperatures, Computer simulation, Copper alloys, High pressure (Technology), Composite materials, Boron nitride

"This study was supported by the National Research Foundation (NRF) of Korea, funded by the Ministry of Education, Science and Technology (NRF-2016M2B2A9A02943809 and NRF-2015R1D1A1A01060718, 2017R1A2B3002307), and by Leading Foreign research Institute Recruitment Program through NRF, funded by the Ministry of Science, ICT & Future Planning (MSIP) (2013K1A4A3055679)."


CC BY 4.0 (Attribution), ©2018 The Authors