Structural origins of Johari-Goldstein relaxation in a metallic glass

Liu, Y. H.; Fujita, Takeshi; Aji, Daisman P. B.; Matsuura, Makoto; Chen, Luyang

doi:10.1038/ncomms4238

Cited by 166 publications

(96 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This result is surprisingly consistent with the X-ray experiments in metallic glasses 50,51 , showing that the b relaxation originates from highly localized bond switching. More importantly, the individual b processes are found insensitive to the overall properties of the system.…”

Section: Correlation Between Different Triggers and Pel Constructionsupporting

confidence: 90%

How thermally activated deformation starts in metallic glass

2014

View full text Add to dashboard Cite

The studies on dynamics and deformation in glassy materials are particularly challenging because of their strongly disordered atomic structure. Here, by probing the changes in the atomic displacements and stresses at saddle points of the potential energy landscape, we show that thermally activated deformation is triggered by subnano-scale rearrangements of a small number of atoms, typically less than 10 atoms. The individual triggers are invariant of the cooling history or elastic structure of the system. However, the organizations between different trigger centres can be varied and are related to the overall stability of the system. This finding allows a semi-quantitative construction of the potential energy landscape and brings a new perspective to the study of the mechanical properties of glasses.

show abstract

Section: Correlation Between Different Triggers and Pel Constructionsupporting

confidence: 90%

How thermally activated deformation starts in metallic glass

2014

View full text Add to dashboard Cite

show abstract

“…Moreover, the low-temperature aging observed here can not be explained in simple terms of free volume, but rather comprises distinct changes in the CSRO though local optimization of atomic pair interactions. These findings are consistent with the emergent idea that low-temperature aging and the slow β relaxation can be characterized by short-range atomic rearrangements in loosely packed or weakly bonded regions [63,64]. In this section, we will discuss some important chemical aspects associated with the observed low-temperature aging behavior in this particular metallic glass system.…”

Section: B Atomic-scale Structural Changes During β Relaxationsupporting

confidence: 80%

βrelaxation and low-temperature aging in a Au-based bulk metallic glass: From elastic properties to atomic-scale structure

et al. 2014

View full text Add to dashboard Cite

The slow β relaxation is understood to be a universal feature of glassy dynamics. Its presence in bulk metallic glasses (BMGs) is evidence of a broad relaxation time spectrum that extends to deep within the glassy state. Despite the breadth of research devoted to this phenomenon, its microscopic origin is still not fully understood. The low-temperature aging behavior and atomic structural rearrangements of a Au 49 Cu 26.9 Si 16.3 Ag 5.5 Pd 2.3 BMG are investigated in the regime of the slow β relaxation by employing an ensemble of experimental techniques such as high-intensity synchrotron x-ray scattering, modulated differential scanning calorimetry (MDSC), dynamic mechanical analysis (DMA), impulse excitation, and dilatometry. Evidence of a distinct slow β-relaxation regime is seen in the form of (1) an excess wing of the DMA loss modulus beginning at ∼50• C, (2) a crossover effect of elastic modulus with isothermal aging at 50• C, and (3) a broad, nonreversing and largely irreversible sub-T g endotherm in the MDSC results. Atomic rearrangements occurring at the onset of the measured slow β-relaxation temperature regime were found to be confined mainly to the short-range order length scale while no significant atomic rearrangements occur on the length scale of the medium-range order. Furthermore, evidence is presented that suggests the crossover effect in Young's modulus is due to the evolution of chemical short-range order. These results support the emergent picture of a dynamically heterogeneous glassy structure, in which low-temperature relaxation occurs through atomic rearrangements confined mostly to the short-range order length scale.

show abstract

“…It is known that the flow phenomenon in MG is the percolation of the localized flow units 12,14,21 . To detect the extreme slow hidden flow before yielding or microscopic structural evolution during GLT, we applied Dynamical Mechanical Spectrum (DMS) measurement, which is a sensitive method to detect the viscoelastic properties of MGs [34][35][36] .…”

Section: Resultsmentioning

confidence: 99%

“…Apart from the stress-induced instantaneous flow of yield, recent experiments and numerical simulations also demonstrated that a glass subject to stress, which is much smaller than its normal yield strength, can also undergo an extreme slow flowing, which is hard to be detected within a short period of time due to the slowness [4][5][6][7] . On the other hand, the universal nano-scaled localized b-relaxation in metallic glassy state has been observed before the large-scale a-relaxation, which has been demonstrated to be related to the nano-scaled microscopic hidden flowing phenomenon [8][9][10][11][12] . However, the structural origin of the flowing phenomena in metallic glasses (MGs) such as the slow flowing and instantaneous flow of yield, elastic and plastic deformations, the transition between the b-relaxation to the a-relaxation and glass to supercooled liquid transition are not clear yet due to the lack of clear structural information.…”

mentioning

confidence: 99%

Evolution of hidden localized flow during glass-to-liquid transition in metallic glass

et al. 2014

View full text Add to dashboard Cite

For glasses, the structural origin of their flow phenomena, such as elastic and plastic deformations especially the microscopic hidden flow before yield and glass-to-liquid transition (GLT), is unclear yet due to the lack of structural information. Here we investigate the evolution of the microscopic localized flow during GLT in a prototypical metallic glass combining with dynamical mechanical relaxations, temperature-dependent tensile experiments and stress relaxation spectra. We show that the unstable and high mobility nano-scale liquid-like regions acting as flow units persist in the glass and can be activated by either temperature or external stress. The activation of such flow units is initially reversible and correlated with b-relaxation. As the proportion of the flow units reaches a critical percolation value, a mechanical brittle-to-ductile transition or macroscopic GLT happens. A comprehensive picture on the hidden flow as well as its correlation with deformation maps and relaxation spectrum is proposed.

show abstract

Structural origins of Johari-Goldstein relaxation in a metallic glass

Cited by 166 publications

References 35 publications

How thermally activated deformation starts in metallic glass

How thermally activated deformation starts in metallic glass

βrelaxation and low-temperature aging in a Au-based bulk metallic glass: From elastic properties to atomic-scale structure

Evolution of hidden localized flow during glass-to-liquid transition in metallic glass

Contact Info

Product

Resources

About