高强度大塑性纳米玻璃的变形与破坏机理研究

Possessing very high strength and high elastic strain limit, metallic glasses (MGs) show a great potential for a wide range of engineering applications. However, an outstanding issue that hinders their practical applications is the sudden brittle failure via localized shear banding. The focus of research on MGs in the last decade, as a consequence, has been on improving their plasticity. A new type of MG referred to as nanoglass (NG) has been recently proposed. NG may introduce internal networked structures in the form of interfaces that cooperatively act to suppress macroscopic shear localization. However, the high free volume at the glass-glass interfaces also contributes to the softening of strength. In the present project, we will perform molecular dynamics simulations on the tensile fracture of Cu50Zr50 NG with architectured atomic-level structures by using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). We aim to not merely enhance the ductility, but aslo maintain the high strength which is supposed to be one of material advantages. Based on these results, the new design concept of the architectured atomic-level structures will be introduced. The project will pave the way for attaining superior mechanical properties by using architectured materials.

金属玻璃具有高强度等优异性能，从而受到广泛关注。然而，在室温拉伸载荷作用下，金属玻璃沿着单一剪切带发生断裂，几乎没有宏观塑性，这成为其作为结构材料应用的瓶颈。近十年来，金属玻璃领域的研究重心是如何改善其塑性。最近研究表明，在金属玻璃中引入纳米量级的“晶界”（纳米玻璃），可诱发更多的剪切带，从而大大地提高了金属玻璃的塑性。这使纳米玻璃这一新颖材料受到世界的瞩目。但是，晶界的引入虽然可以改善塑性，但却同时也弱化了材料的强度。为了达到双赢的目的，即在提高其塑性的同时，最大限度地保持其高强度的特性,本项目拟采用大规模分子动力学手段，深入研究纳米玻璃的变形与破坏机理，并进一步构筑新型的多层次多结构多组分的纳米玻璃，以得到高强度大塑性的纳米玻璃。为解决困扰金属玻璃多年的难题提供新途径，并为制备和开发高性能、多功能的新构型材料奠定基础。

强度和韧性的权衡一直是材料科学中一个长期存在的问题。在本项目中，我们采用分子动力学方法，系统地研究了具有双粒径大小分布的纳米玻璃结构的拉伸变形及破坏机制。结果表明，可以通过控制纳米玻璃中的双粒径大小分布来调控纳米玻璃的力学性能，为纳米玻璃体系同时具有高强度和高韧性提供了一种系统的设计方法。此外，我们开展拉伸载荷下的分子动力学模拟，评价了金属玻璃/纳米玻璃多层复合材料的力学性能。主要关注纳米玻璃层厚度、层间距以及载荷方向对多层复合材料的强度和失效的影响。该工作表明，由金属玻璃层及厚度合适的纳米玻璃层组成的多层结构能够在保持结构稳定的同时又具有大的塑性变形。这些结果将激发新的高强度超塑性金属玻璃复合材料的发展，拓宽金属玻璃的潜在工程应用。