新型纳米多孔金属玻璃复合材料的变形与破坏机理

Bulk metallic glasses (BMGs) have received extensive attention as potential structural materials due to their superior mechanical properties such as high strength and large elastic strain. However, their main drawback is their propensity for catastrophic failure in tensile loading by the instantaneous propagation of shear bands (SBs), which significantly limits their structural applications. Considerable efforts have been made towards eliciting and improving ductility in BMGs. Among them, it has been demonstrated that a transition from a strong-yet-brittle to a stronger-and-ductile state by size reduction of metallic glasses to hundreds of nanometers. In the present project, we focus on constructing a series of novel BMGs composites with the pore sizes in the nanometer regime. By using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), we will perform molecular dynamics (MD) simulations on the nanoporous metallic glasses and their nanolaminate composites to investigate their deformation and failure mechanisms. Based on these results, we aim to design the strong-and-ductile BMGs composites with nanoscale cellular structures. The project will provide new strategies for solving the problem of ductility in BMGs, and pave the way for attaining high performance and superior mechanical properties and by using composite materials.

块体金属玻璃虽然具有高的断裂强度以及高的弹性应变极限，但室温塑性极差，易发生灾难性脆性断裂。但是纳米尺度的金属玻璃具有非常好的塑性变形能力。本项目拟把纳米尺度的微观结构引入到块体金属玻璃中，提出用纳米孔洞与块体金属玻璃相结合来构建新型纳米多孔金属玻璃复合材料。首先，利用大规模分子动力学模拟手段，从原子尺度上揭示纳米蜂窝金属玻璃、纳米蜂窝金属玻璃夹心板结构的变形与破坏机理。在此基础上，构建一些新型的纳米多孔金属玻璃复合材料，为解决困扰金属玻璃多年的难题提供新途径，为制备高性能、多功能的金属玻璃复合材料奠定理论基础。

金属玻璃虽然具有高的断裂强度以及高的弹性应变极限，但室温塑性极差，易发生灾难性脆性断裂，严重限制了金属玻璃的应用范围。纳米多孔金属玻璃兼具金属玻璃的优异性能和微结构力学性能可控的特性，有望发展成新型结构及功能一体化的材料。本项目把纳米尺度的微观结构引入到块体金属玻璃中，构建了纳米多孔金属玻璃以及具有褶皱微结构特征的金属玻璃。采用大规模分子动力学方法，研究了纳米多孔金属玻璃及具有褶皱微结构特征的金属玻璃的力学性能和失效机理。此外，开展了热压处理对金属玻璃回春效果及其力学性能的研究工作。研究结果表明：（a）纳米多孔金属玻璃具有轻质、高强、高韧的拉伸力学性能；（b）表面能导致纳米多孔金属玻璃具有拉压不对称的性能；（c）纳米多孔金属玻璃中韧带的失效形式显著依赖于韧带的长细比及其受力情况；（d）通过褶皱结构引入应力梯度可以有效地改善金属玻璃的韧性；（d）金属玻璃不仅可以通过正压高退火温度实现回春，而且可以通过负压低退火温度达到回春效果。本项目为纳米多孔金属玻璃的失效机理提供了原子水平的认识，为纳米多孔金属玻璃的设计和应用提供了新的思路。同时，也为金属玻璃增韧提供了一种新的方法。