| 초록 |
While nanocrystalline (NC) aluminum(Al) exhibit superior strength to conventional microcrystalline metals, their thermal instability has hampered their application at high temperatures. Herein, we propose two-dimensional (2D) boron nitride nanosheets (BNNS) 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 oC (~0.9 Tm, where Tm is the melting point of Al), preventing a strength drop at the high temperature. Finally, the Zener pinning model along 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. It 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. |
