School of Advanced Materials Engineering, Kookmin University, Seoul, 02707, Republic of Korea.
Nuclear Materials Safety Research Division, Korea Atomic Energy Research Institute, Daejeon, 34057, Republic of Korea.
Sci Rep. 2018 Jan 25;8(1):1614. doi: 10.1038/s41598-018-20150-5.
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 T, where T 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.
虽然纳米晶（NC）金属表现出比传统微晶金属更高的强度，但它们的热不稳定性阻碍了它们在高温下的应用。在此，二维（2D）氮化硼纳米片（BNNS）被提议作为增强材料，以提高 NC Al 的强度和热稳定性。通过将晶粒从600nm 细化至40nm，纯 Al 的强度从 80MPa 提高到 468MPa，通过掺入 2vol%的 BNNS，其强度进一步提高到 685MPa。此外，发现在 580°C（~0.9T，其中 T 是 Al 的熔点）下，少量 BNNS 可有效抑制 NC Al 的晶粒生长，从而防止高温下强度下降。最后，利用 Zener 钉扎模型结合相场模拟定性分析了 BNNS 对晶界钉扎的影响，其影响与增强体的体积、形状和取向有关。该模型表明，二维增强体的钉扎力远高于球形颗粒。因此，2D BNNS 为开发用于高温结构应用的 Al 基纳米复合材料提供了可能性。
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