Xianjun Kong, Xinbo Hu, Minghai Wang, Yaohui Zheng, Ning Hou
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引用次数: 0
摘要
本研究通过实验和分子动力学(MD)研究了块状金属玻璃(BMG)在纳米压痕过程中的变形行为。研究建立了剪切转化区(STZ)形成与锯齿流动力学之间的关系,以解释 BMG 的变形特征演变。研究发现,随着峰值载荷的增加,硬度和弹性模量显著降低。通过分析不同峰值载荷下的蠕变位移曲线和应力指数,还揭示了室温下的蠕变行为。此外,创新性地利用剪切应力滴进一步统计分析了锯齿流行为。在较低载荷下,锯齿状滞留的发生是由于能量超过了流动单元激活所需的势垒,最终以动能的形式释放出来。在较高载荷下,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)态动态特征,同时还观察到 ISE 现象。结果还表明,球形压头的剪切变形更为明显,剪切带与下压方向成 45° 角。并基于合作剪切模型(CSM)理论,估算了STZ的大小,验证了STZ的增量更容易产生更强的塑性应变来耗散STZ,最终导致完全塑性变形。结合五折对称性和梯度原子,当载荷速率较低时,大多数具有五折对称性(LFFS>0.5)的原子具有更强的抗塑性变形能力。
Nanoindentation-induced serrated flow behavior and deformation mechanism in metallic glass: A combined experiments and molecular dynamics simulation
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.
期刊介绍:
The Journal of Alloys and Compounds is intended to serve as an international medium for the publication of work on solid materials comprising compounds as well as alloys. Its great strength lies in the diversity of discipline which it encompasses, drawing together results from materials science, solid-state chemistry and physics.