Ultrasonic-assisted plastic flow in a Zr-based metallic glass

Abstract

Ultrasonic vibration can be used for the micromolding of metallic glasses (MGs) due to stress-softening and fast surface-diffusion effects. However, the structural rearrangement under ultrasonic vibration and its impact on the mechanical response of metallic glasses remain a puzzle. In this work, the plastic flow of the Zr 35 Ti 30 Cu 8.25 Be 26.75 metallic glass with the applied ultrasonic-vibration energy of 140 J was investigated by nanoindentation. Both Kelvin and Maxwell-Voigt models have been adopted to analyze the structural evolution during the creep deformation. The increase of the characteristic relaxation time and the peak intensity of relaxation spectra can be found in the sample after ultrasonic vibration. It effectively improves the activation energy of atomic diffusion during the glass transition (E g ) and the growth of the crystal nucleus (E p ). A more homogenous plastic deformation with a weak loading-rate sensitivity of stress exponent is observed in the ultrasonic-vibrated sample, which coincides with the low pile-up and penetration depth as shown in the cross profile of indents. The structural rearrangement under resonance actuation demonstrated in this work might help us better understand the defect-activation mechanism for the plastic flow of amorphous systems.

Rejuvenation-to-Relaxation Transition Induced by Elastostatic Compression and Its Effect on Deformation Behavior in a Zr-Based Bulk Metallic Glass

“…Similar loading rate dependent behavior has been observed in the pre-compression treated samples as indicated in Figure 6b,c. Two characteristic relaxation peaks have also been found in the relaxation spectrum of many other BMGs such as Fe- [44,47], Zr-based BMGs [48], which is in good agreement with present study. Based on the core-shell model [45], the defects with more free volume are able to dissipate the stress concentrates in the elastic matrix by consuming a long relaxation time.…”

Polyamorphism mediated by nanoscale incipient concentration wave uncovering hidden amorphous intermediate state with ultrahigh modulus in nanostructured metallic glass

“…The present polyamorphic transitions unveil a hidden intermediate state with an unusually high modulus, which opens a new avenue toward advanced MGs with super-mechanical performances by tailoring topological/chemical heterogeneity at nanoscale and supra-nanometer structure engineering. Since chemical heterogeneity, local composition fluctuation, and nanoscale phase separation are facile to create in MGs [64][65][66][67][68][69][70][71], the steplike polyamorphism may exist in other systems.…”

Recent development of chemically complex metallic glasses: from accelerated compositional design, additive manufacturing to novel applications

“…Those liquid-like units can largely absorb the high-frequency vibration energy and enhance the mobility of the atoms due to the nature of viscoelasticity and low stiffness, which can loosen the densely packed clusters and extend the liquid-like regions. This variation of the amorphous structure will induce significantly softening behavior and viscous flow of MGs [146][147][148][149]. Based on this mechanism, the ultrasonic AM process can be applied to the fast cold fusion of BMGs at a very low pressure.…”