Relaxation and Strain-Hardening Relationships in Highly Rejuvenated Metallic Glasses

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.

Atomistic Insight into Grain Boundary Deformation Induced Strengthening in Layer-Grained Nanocrystalline Al

“…In the extreme case where the GB spacing approaches zero, the nanocrystals become amorphous, and amorphous crystals may also exhibit strain hardening during deformation. In amorphous materials, there are no dislocations, and strain hardening occurs through the movement and rearrangement of atomic clusters. − The deformation mechanism of GBs is similar to these mechanisms.…”