Abstract
In this work, the deformation of Zr2Cu metallic glass (MG) under uniaxial tensile stress was investigated at the atomic level using a series of synchrotron radiation techniques combined with molecular dynamics simulation. A new approach to the quantitative detection of free volumes in MGs was designed and it was found that free volumes increase in the elastic stage, slowly expand in the yield stage, and finally reach saturation in the plastic stage. In addition, in different regions of the MG model, free volumes exhibited inhomogeneity under stress, in terms of size, density, and distribution. In particular, the expansion of free volumes in the center region was much more rapid than those in the other regions. It is interesting that the density of free volumes in the center region abnormally decreased with strain. It was revealed that the atomic-level stress between different regions may contribute to the inhomogeneity of free volumes under stress. In addition, the inhomogeneous change of free volumes during the deformation was confirmed by the evolution of local atomic shear strains in different regions. The present work provides in-depth insight into the deformation mechanisms of MGs.
Highlights
Metallic glasses (MGs) have many potential applications due to their unique physical, chemical, and mechanical properties, such as relatively high levels of strength and hardness [1,2,3], a superior large elastic limit [4,5], excellent corrosion resistance, high wear resistance [6]
The underlying deformation mechanisms of MGs were investigated from the free volume aspect
It was revealed that free volumes expanded with increased of strain and this expansion stopped in the plastic stage
Summary
Metallic glasses (MGs) have many potential applications due to their unique physical, chemical, and mechanical properties, such as relatively high levels of strength and hardness [1,2,3], a superior large elastic limit [4,5], excellent corrosion resistance, high wear resistance [6]. Compared with crystalline alloys, there is still a challenge to reveal the deformation mechanisms of MGs due to their disordered nature [7,8,9]. To address this issue, various specific structural concepts or models have been proposed, including shear transformation zones (STZs), flow units, and flexible volumes [10,11,12,13,14]. It was proposed that deformation occurs preferentially in some local regions, referred to as STZs [11], which are characterized by a lower density of atomic packing [10]. It is difficult to experimentally measure the shear localization at the atomic scale due to the extremely short time and the very small scale lengths involved [16]
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