In this study, the deformation behaviors of bulk metallic glass (BMG) during the nanoindentation are presented via the experiments and molecular dynamics (MD). The relationship between shear transformation zone (STZ) formation and serrated flow dynamics are developed to explain the deformation characterization evolution of BMG. It is found that as the peak load increases, the hardness and elastic modulus significantly decrease. Creep behavior at room temperature was also revealed by analyzing the creep displacement curve and the stress index under different peak loads.The accumulation of free volume during the deformation process promotes more uniform creep deformation. Furthermore, the serrated flow behaviors were analyzed innovatively using the shear stress drops further statistically. At lower loads, the occurrence of serrated retention is due to energy exceeding the potential barrier required for flow unit activation, ultimately released in the form of kinetic energy. At higher loads, the transition from intermittent curve to smooth curve exhibits a typical self-organized critical (SOC) state dynamic characteristics, and ISE phenomenon is also observed. The results also suggested that the shear deformation of the spherical indenter is more pronounced, with the shear band forming at a 45° angle to the direction of the downward pressure. And based on the Cooperative shear model (CSM) theory, the STZ size was estimated and verify that the increment of STZ makes it easier to generate stronger plastic strain to dissipate STZ, ultimately leading to complete plastic deformation. Combining five fold symmetry and gradient atoms, the majority of atoms with five fold symmetry (LFFS>0.5) have stronger resistance to plastic deformation when the load rate is low.

中文翻译：

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金属玻璃中纳米压痕引起的锯齿状流动行为和变形机制：实验与分子动力学模拟相结合


在这项研究中，通过实验和分子动力学（MD）展示了块体金属玻璃（BMG）在纳米压痕过程中的变形行为。研究了剪切转变区 (STZ) 形成与锯齿状流动动力学之间的关系，以解释 BMG 的变形特征演化。研究发现，随着峰值载荷的增加，硬度和弹性模量显着下降。通过分析不同峰值载荷下的蠕变位移曲线和应力指数，揭示了室温下的蠕变行为。变形过程中自由体积的积累促进了蠕变变形更加均匀。此外，还利用剪切应力降进一步进行统计分析，对锯齿状流动行为进行了创新性分析。在较低负载下，锯齿状滞留的发生是由于能量超过流动单元激活所需的势垒，最终以动能的形式释放。在较高负载下，从间歇曲线到平滑曲线的过渡表现出典型的自组织临界（SOC）状态动态特性，并且还观察到ISE现象。结果还表明，球形压头的剪切变形更加明显，剪切带与向下压力的方向成45°角。并基于协同剪切模型（CSM）理论估算了STZ的尺寸，并验证了STZ的增量使得更容易产生更强的塑性应变来消散STZ，最终导致完全塑性变形。将五重对称性和梯度原子结合起来，大多数五重对称性原子（LFFS>0.5）在低载荷率时具有更强的抗塑性变形能力。