Relaxation and Strain-Hardening Relationships in Highly Rejuvenated Metallic Glasses.

Xudong Yuan,Jürgen Eckert,Daniel Şopu,Kaikai Song

doi:10.3390/ma15051702

Abstract

One way to rejuvenate metallic glasses is to increase their free volume. Here, by randomly removing atoms from the glass matrix, free volume is homogeneously generated in metallic glasses, and glassy states with different degrees of rejuvenation are designed and further mechanically tested. We find that the free volume in the rejuvenated glasses can be annihilated under tensile or compressive deformation that consequently leads to structural relaxation and strain-hardening. Additionally, the deformation mechanism of highly rejuvenated metallic glasses during the uniaxial loading–unloading tensile tests is investigated, in order to provide a systematic understanding of the relaxation and strain-hardening relationship. The observed strain-hardening in the highly rejuvenated metallic glasses corresponds to stress-driven structural and residual stress relaxation during cycling deformation. Nevertheless, the rejuvenated metallic glasses relax to a more stable state but could not recover their initial as-cast state.

Highlights

Metallic glasses (MGs) are obtained by fast cooling from the melt to avoid crystallization and exhibit a disordered structure with higher-energy states [1,2,3]
Rejuvenation is an effective way to inspire the structure of MGs to restore flexibility with the increase of free volume and enthalpy [17,18,19,20] and it is regarded as a promising approach for tuning the deformability of
Extreme rejuvenated MGs could even show strain-hardening that was associated with structural relaxation when loaded in uniaxial tension or compression which can be regarded as a return from the rejuvenated state [21]

Summary

Introduction

Metallic glasses (MGs) are obtained by fast cooling from the melt to avoid crystallization and exhibit a disordered structure with higher-energy states [1,2,3]. Extreme rejuvenated MGs could even show strain-hardening that was associated with structural relaxation when loaded in uniaxial tension or compression which can be regarded as a return from the rejuvenated state [21]. A systematic understanding of the relationship between the degree of rejuvenation and deformation behavior in MGs is missing and an atomistic and mechanistic explanation for experimental observations is required. MD simulations allows to quantitatively control the fraction of free volume into the glass matrix and, provide a systematic strategy to manipulate the degree of rejuvenation in MGs [28]. We present MD computer simulations of the deformation behavior of MGs with a controlled degree of rejuvenation. Loading–unloading cycling tensile tests are simulated and the mechanism of strain-hardening in the highly rejuvenated MG is highlighted

Samples Preparation

Deformation Tests

Results and Discussions

Conclusions