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金属玻璃(MGs)的剪切带行为与其微观结构不均匀性密切相关.传统分子动力学(MD)模拟因超快冷却速率导致MGs结构保留了更多液体特征,而交换原子的蒙特卡洛(SMC)方法能够在模拟上制备出可匹配实验室时间冷却速度的低能态金属玻璃.本研究通过SMC结合MD方法,构建软硬相分布可控的Cu50Zr50金属玻璃样品,揭示纳米尺度结构不均匀性对剪切带萌生与扩展的调控机制.由MD制备的软相中二十面体有序团簇含量较少,优先激活塑性事件,促进应力重新分布,与邻近硬相一起响应对剪切带扩展起协同作用.MC制备的硬相区由于其高密度的二十面体团簇的含量,使得应力局域集中,形成窄剪切带.通过调控硬相体积分数,复合样品发生由韧到脆转变.此外,在保持硬相百分比不变的前提下,不同序构策略可以改变非晶的力学行为:离散硬相的分布能够增加样品的稳定性,推迟剪切带的产生;硬相包围软相的策略能够促进样品中产生二次剪切带,使得剪切带区域相对非局域化.该研究结果揭示了软硬区结构不均匀性对非晶合金力学性能的影响,以及为采用序构方法设计金属玻璃力学性能提供了可能的理论指导.Shear banding behavior of metallic glasses (MGs) strongly correlates with the microstructural heterogeneity. Understanding how the nucleation and propagation of shear bands governed by the nanoscale structural heterogeneity are crucial for designing high-performance MGs. Herein, we utilized conventional Molecular dynamics (MD) and swap Monte Carlo (SMC) simulations to construct two phases of CuZr metallic glasses: one the soft phase with a high cooling rate about 1013 K/s, and the other one the hard phase with a extremely low cooling rate in simulations about 104 K/s. The soft phase is more prone to the plastic deformation due to the poor population of icosahedral clusters; the hard phase is of more icosahedral clusters, promoting shear localization once the shear bands form inside. We found a ductileto-brittle transition in the soft-and-hard phase ordered MGs with the increment of the hard-region fraction c. Additionally, the strategy of how to order these two phases could strongly affect the mechanical behavior of MGs. Dispersive and isolated hard-regions can enhance the mechanical stability of MGs, delaying the occurrence of shear banding. Instead, surrounding soft regions by hard regions can induce a secondary shear band that formed through the reorientation of plastic zones under constrained deformation, leading to a relatively more delocalized plastic deformation zones. The work unveils that the structural heterogeneity achieved by tuning the topology of soft and hard phase can significantly change the mechanical performance of MGs, and this could guide the design of metallic glasses with controllable structures via architectural ordering strategies.
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Keywords:
- Metallic glasses /
- Order modulation /
- Molecular-dynamics simulations /
- Shear banding
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