While metallic glasses (MGs) usually fracture catastrophically under uniaxial loading, external confinement like coating has been proved quite effective for improving the plasticity. The positive effect of confinement was mainly attributed to the lateral confining stress on the interface between sample and confinement, which impedes the excess propagation of shear bands and promotes their multiplication. Here we show that, even though there is no contact between the MG and the confinement, the brittle fracture can be effectively suppressed. Three dimensional (3D) high resolution X-ray tomography observations successfully captured the shear-band cracking evolution and confirmed that the external confinement caused the change of shear-band fracture mode. Analysis on the thermodynamics and kinetics of shear banding in the confined MG shows that the confinement extremely reduces the shear velocity, contributes to the shear band arrest, and largely lowers the energy release rate, leading to the increase of the shear stability and the resistance to instant fracture. Finally, the mechanisms of confinement effect on the plastic deformation in various confined MG systems were summarized. These results suggest new understandings on the effect of confinement for the fracture of MG composites or coated MG structures, and on the mechanisms of shear-band cracking and fracture in different MG loading systems.

虽然金属玻璃（MGs）通常在单轴载荷下会发生灾难性的断裂，但事实证明像涂层这样的外部限制对于提高可塑性非常有效。约束的积极作用主要归因于样品与约束之间界面上的侧向约束应力，这阻碍了剪切带的过度传播并促进了剪切带的繁殖。在这里我们表明，即使MG和约束之间没有接触，也可以有效地抑制脆性断裂。三维（3D）高分辨率X射线断层扫描观察成功捕获了剪切带破裂的演变，并确认了外部限制导致剪切带断裂模式的改变。对密闭式MG的剪切带的热力学和动力学分析表明，该约束极大地降低了剪切速度，有助于剪切带的阻滞，并大大降低了能量释放速率，从而导致剪切稳定性和抗冲击性的提高。即时骨折。最后，总结了各种密闭MG系统中限制作用对塑性变形的作用机理。这些结果提出了对封闭对MG复合材料或涂层MG结构的断裂的影响，以及对不同MG加载系统中的剪切带破裂和断裂机理的新认识。导致剪切稳定性和抗瞬间断裂性的提高。最后，总结了各种密闭MG系统中限制作用对塑性变形的作用机理。这些结果提出了对封闭对MG复合材料或涂层MG结构的断裂的影响，以及对不同MG加载系统中剪切带破裂和断裂机理的新认识。导致剪切稳定性和抗瞬间断裂性的提高。最后，总结了各种密闭MG系统中限制作用对塑性变形的作用机理。这些结果提出了对封闭对MG复合材料或涂层MG结构的断裂的影响，以及对不同MG加载系统中剪切带破裂和断裂机理的新认识。