In this study, we report the grain boundary driven mechanical behavior of 2 polycrystalline ultra‐high‐temperature ceramics (UHTCs), zirconium diboride (ZrB₂) and zirconium carbide (ZrC) with zirconium diboride (ZrC‐ZrB₂). These nanocomposites were investigated using large‐scale molecular dynamics simulations. First, the atomistic models of the polycrystalline ZrB₂ and ZrC‐ZrB₂ nanocomposites were subjected to tensile loading to determine their elastic constants and tensile strengths. It was found that the presence of nanoparticles imparts an insignificant effect on the mechanical properties of ZrB₂. It has also been observed that the failure mechanisms of both the ZrB₂ and ZrC‐ZrB₂ nanocomposite are driven by grain boundary deformation. At any instant during the applied load transfer, local tensile stress distribution data indicate that atomic stress becomes much higher near the grain boundaries compared to other locations. The authors performed additional sets of simulations to obtain tensile and shear properties of grain boundary material. When these properties were compared with the adjacent single crystal and overall polycrystalline material properties, it was found that the shear strength and stiffness of the grain boundary materials are significantly lower than the single crystal or polycrystal ZrB₂. It is believed that the overall deformation and failure properties of ZrB₂ and its composite are controlled by the properties of grain boundary. Hence, the addition of nanoparticles played an insignificant role on the mechanical properties of ZrB₂.

中文翻译：

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ZrB2和ZrC-ZrB2纳米复合材料的晶界驱动力学性能：分子模拟研究

在这项研究中，我们报告了两种多晶超高温陶瓷（UHTC），二硼化锆（ZrB ₂）和碳化锆（ZrC）和二硼化锆（ZrC-ZrB ₂）的晶界驱动力学行为。这些纳米复合材料进行了大规模的分子动力学模拟研究。首先，对多晶ZrB ₂和ZrC-ZrB ₂纳米复合材料的原子模型进行拉伸载荷，以确定其弹性常数和拉伸强度。发现纳米颗粒的存在对ZrB ₂的机械性能影响不大。还观察到ZrB ₂和ZrC-ZrB的失效机理₂纳米复合材料是由晶界变形驱动的。在施加的载荷传递过程中的任何时刻，局部拉伸应力分布数据表明，与其他位置相比，晶界附近的原子应力变得更高。作者进行了额外的一组模拟，以获得晶界材料的拉伸和剪切性能。当将这些性质与相邻的单晶和整体多晶材料的性质进行比较时，发现晶界材料的剪切强度和刚度显着低于单晶或多晶ZrB ₂。据信ZrB ₂的整体变形和破坏特性其复合材料受晶界特性控制。因此，纳米粒子的添加对ZrB ₂的机械性能起着微不足道的作用。