Abstract Metallic glass usually ruptures at a small strain by forming single dominant shear band under tension at room temperature. Experiments have shown that multiple shear bands can be induced in metallic glass film by a ductile metallic substrate, and the ductility of the film can be elevated significantly. However, the mechanism behind remains unsolved. Here we established a computational model to investigate the effect of a Ni substrate on the deformation of a Ni-P amorphous film. The shear band evolution in the film was described by a free volume-based constitutive theory, while the deformation of the Ni substrate was simulated by a dislocation density-based model. The film/substrate interface was modeled by a cohesive zone law. In the simulations, the shear band evolution and the stress in the film can be measured directly, which is difficult to achieve in experiments. Our simulations show that multiple shear bands have been formed in the substrate-supported metallic glass film if the film thickness hf is less than 10 µm. The thinner the film is, the more the shear bands the film has. The number of shear bands can reach as high as 16 as hf is refined down to 2.5 µm. The generation of the multiple shear bands alleviated the strong strain-softening as observed in free standing film, as clearly shown in the stress-strain response of the thin film in the film/substrate system. The suppressed strain-softening induces significantly enhanced tensile ductility in the amorphous film. The tensile ductility of the 2.5 µm-thick film on the Ni substrate can reach as high as 13.3%, which is much higher than that of the corresponding freestanding film, i.e., 3.1%. The proposed computational model has been validated by the coincident stress-strain responses between simulations and experiments. The findings revealed that the enhanced tensile ductility originates from the shear band multiplication-induced strain delocalization in the amorphous film due to the constraint of the metallic substrate.

中文翻译：

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剪切带倍增引起金属衬底非晶薄膜的强应变离域和高拉伸延展性

摘要 金属玻璃通常在室温下在张力作用下形成单一的主导剪切带，从而在小应变下破裂。实验表明，延展性金属基体可在金属玻璃薄膜中诱发多个剪切带，显着提高薄膜的延展性。然而，背后的机制仍未解决。在这里，我们建立了一个计算模型来研究 Ni 衬底对 Ni-P 非晶膜变形的影响。薄膜中的剪切带演化由基于自由体积的本构理论描述，而镍基体的变形由基于位错密度的模型模拟。薄膜/基材界面由内聚区定律建模。在模拟中，剪切带演化和薄膜中的应力可以直接测量，这在实验中是很难实现的。我们的模拟表明，如果薄膜厚度 hf 小于 10 µm，则在基板支撑的金属玻璃薄膜中形成了多个剪切带。薄膜越薄，薄膜的剪切带越多。当 hf 细化到 2.5 µm 时，剪切带的数量可高达 16 个。多剪切带的产生减轻了在独立式薄膜中观察到的强烈应变软化，如薄膜/基板系统中薄膜的应力-应变响应所示。受抑制的应变软化导致非晶膜的拉伸延展性显着增强。Ni基板上2.5μm厚的薄膜的拉伸延展性可高达13.3%，远高于相应的独立薄膜的3.1%。所提出的计算模型已通过模拟和实验之间一致的应力应变响应得到验证。研究结果表明，增强的拉伸延展性源于由于金属基材的约束，非晶膜中剪切带倍增引起的应变离域。