Dai Kaiqing, Zhang Chun, Lu Wenjun, Li Jianjun
College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China.
State Key Laboratory of Precision Manufacturing for Extreme Service Performance, Central South University, Changsha 410083, China.
Nanomaterials (Basel). 2024 Mar 20;14(6):546. doi: 10.3390/nano14060546.
Extensive research has shown that nanolayered structures are capable of suppressing the shear banding in metallic glass in nanoindentation experiments. However, the specific mode and mechanism of the shear banding underneath the indenter remains unknown. Also, the quantification of shear banding-induced strain localization is still a challenge. Herein, the size-dependent shear banding behavior of a CuTiZrNb high-entropy alloy-based nanolayered glass with individual layer thicknesses () ranging from 5 to 80 nm was systematically investigated by nanoindentation tests. It was found that the hardness of the designed structure was almost size-independent. Yet, a clear transition in the deformation modes from the cutting-like shear bands to the kinking-like ones was discovered as decreased to 10 nm. Moreover, multiple secondary shear bands also appeared, in addition to the primary ones, in the sample with = 10 nm. The transition leads to an obvious strain delocalization, as clearly illustrated by the proposed theoretical model, which is based on the assumption of a pure shear stress state to quantify the shear banding-induced strain localization. The strain delocalization results from the higher density of amorphous/amorphous interfaces that exhibit the change in morphology with a refined layered glass structure.
广泛的研究表明，在纳米压痕实验中，纳米层状结构能够抑制金属玻璃中的剪切带。然而，压头下方剪切带的具体模式和机制仍然未知。此外，对剪切带引起的应变局部化进行量化仍是一项挑战。在此，通过纳米压痕试验系统地研究了具有5至80nm单层厚度（）的CuTiZrNb高熵合金基纳米层状玻璃的尺寸依赖性剪切带行为。发现设计结构的硬度几乎与尺寸无关。然而，当降至10nm时，发现变形模式从类似切削的剪切带明显转变为类似扭结的剪切带。此外，在单层厚度为10nm的样品中，除了主剪切带之外还出现了多个二次剪切带。如所提出的理论模型所示，这种转变导致明显的应变非局部化，该理论模型基于纯剪切应力状态的假设来量化剪切带引起的应变局部化。应变非局部化源于更高密度的非晶/非晶界面，这些界面随着细化的层状玻璃结构而呈现形态变化。
