IFW Dresden, Institut für Komplexe Materialien, Helmholtzstraße 20, D-01069 Dresden, Germany.
Politehnica University of Timisoara , P-ta Victoriei 2, RO-300006 Timisoara, Romania.
Nano Lett. 2016 Jul 13;16(7):4467-71. doi: 10.1021/acs.nanolett.6b01636. Epub 2016 Jun 6.
When reducing the size of metallic glass samples down to the nanoscale regime, experimental studies on the plasticity under uniaxial tension show a wide range of failure modes ranging from brittle to ductile ones. Simulations on the deformation behavior of nanoscaled metallic glasses report an unusual extended strain softening and are not able to reproduce the brittle-like fracture deformation as found in experiments. Using large-scale molecular dynamics simulations we provide an atomistic understanding of the deformation mechanisms of metallic glass nanowires and differentiate the extrinsic size effects and aspect ratio contribution to plasticity. A model for predicting the critical nanowire aspect ratio for the ductile-to-brittle transition is developed. Furthermore, the structure of brittle nanowires can be tuned to a softer phase characterized by a defective short-range order and an excess free volume upon systematic structural rejuvenation, leading to enhanced tensile ductility. The presented results shed light on the fundamental deformation mechanisms of nanoscaled metallic glasses and demarcate ductile and catastrophic failure.
当将金属玻璃样品的尺寸减小到纳米尺度时，单轴拉伸下的塑性实验研究显示出从脆性到韧性的多种失效模式。对纳米尺度金属玻璃变形行为的模拟报告了异常的应变软化扩展，并且无法再现实验中发现的类似脆性的断裂变形。我们使用大规模分子动力学模拟，提供了对金属玻璃纳米线变形机制的原子理解，并区分了对塑性的外在尺寸效应和纵横比贡献。开发了用于预测从韧性到脆性转变的临界纳米线纵横比的模型。此外，通过系统的结构恢复，可以将脆性纳米线的结构调整为具有缺陷短程有序和过剩自由体积的较软相，从而提高拉伸延展性。所提出的结果阐明了纳米尺度金属玻璃的基本变形机制，并划定了韧性和灾难性失效。
