Yielding transition in stable glasses periodically deformed at finite temperature

Abstract

The effect of glass stability on the yielding transition and mechanical properties of periodically deformed binary glasses is investigated using molecular dynamics simulations. We consider a binary mixture first slowly cooled below the glass transition temperature and then mechanically annealed to deeper energy states via smallamplitude oscillatory shear deformation. We show that upon increasing glass stability, the shear modulus and the yielding peak during startup continuous deformation increase towards plateau levels. It is found that during the strain amplitude sweep, the yielding transition occurs at higher amplitudes and it becomes more abrupt in deeply annealed glasses. The processes of initiation and formation of a shear band are elucidated via the spatiotemporal analysis of nonaffine displacements of atoms. These results are important for thermo-mechanical processing of highly stable amorphous alloys.

Annealing effects of multidirectional oscillatory shear in model glass formers

“…2 (ii), we plot the average energy that the system is allowed to relax to, via unidirectional cyclic shear, as measured just before a pulse. The system exhibits an initial, logarithmic annealing in the energy, as has also been observed in finite temperature systems [13,25]. In the inset, we plot the change in energy after each pulse, which displays a scaling consistent with compaction: ∆E ∼ N −1 pulse .…”

Relaxation dynamics in amorphous alloys under asymmetric cyclic shear deformation

“…In this case, the binary mixture was first slowly cooled from 𝑇 𝐿𝐽 = 1.0 𝜀∕𝑘 𝐵 to 0.3 𝜀∕𝑘 𝐵 with the rate of 10 −5 𝜀∕𝑘 𝐵 𝜏 at 𝜌 = 1.2 𝜎 −3 , then periodically deformed for 5000 cycles, and finally cooled to 𝑇 𝐿𝐽 = 0.01 𝜀∕𝑘 𝐵 at 𝜌 = 1.2 𝜎 −3 . In the previous study [53], it was shown that this preparation procedure leads to a relatively stable glass with the potential energy 𝑈 ≈ −8.352 𝜀 in the undeformed state. Fig.…”

Fatigue Behavior of Cu-Zr Metallic Glasses under Cyclic Loading

“…Whereas poorly annealed glasses tend to relax when subjected to small-amplitude cyclic shear [12,22,24,27,29], well-annealed amorphous alloys can be rejuvenated during a number of cycles before yielding at strain amplitudes above a critical point [33,35,42]. The yielding transition in periodically deformed glasses typically proceeds through the formation of shear bands that are initiated either at open boundaries [14,15,26,36,39] or in the bulk of the computational domain in case of periodic boundary conditions [20,21,23,24,28,33,37,40,42]. In the vicinity of a critical strain amplitude, the number of cycles until the yielding transition depends on temperature [33], preparation history [20,28,37,40], strain amplitude [15,20,21,33], deformation protocol [30], and loading frequency [15].…”

“…The yielding transition in periodically deformed glasses typically proceeds through the formation of shear bands that are initiated either at open boundaries [14,15,26,36,39] or in the bulk of the computational domain in case of periodic boundary conditions [20,21,23,24,28,33,37,40,42]. In the vicinity of a critical strain amplitude, the number of cycles until the yielding transition depends on temperature [33], preparation history [20,28,37,40], strain amplitude [15,20,21,33], deformation protocol [30], and loading frequency [15]. Notably, it was recently demonstrated that fatigue failure in well-annealed binary Lennard-Jones (LJ) glasses occurs after a number of shear cycles that increases as a power-law function when the loading amplitude approaches a critical value [42].…”