Non-exponentiality of structural relaxations in glass forming metallic liquids

Wang, Limin; Chen, Zeming; Zhao, Yue; Liu, Riping; Tian, Yongjun

doi:10.1016/j.jallcom.2010.04.011

Cited by 18 publications

(3 citation statements)

References 77 publications

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“…The average τ(T) derived from central portion of the images, shown in Figure 2(f), is in reasonable agreement with bulk measurements on the same alloy. τ extracted from the bulk increases from ~20 s to ~350 s when the temperature is cooled from Tg + 16 K to Tg, which is consistent with data reported for supercooled metallic glass forming liquids 20,[40][41][42] . τ(T) follows the Arrhenius law over the limited temperature range accessible in ECM, with an activation energy of 3.7 ± 0.3 eV, in good agreement with typical values for bulk metallic glass alloys 43,44 , and the viscosity estimated from the Debye-Stokes Einstein equation is in reasonable agreement with estimates in the literature for the same alloy 45 .…”

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confidence: 89%

Spatially heterogeneous dynamics in a metallic glass forming liquid imaged by electron correlation microscopy

et al. 2018

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Supercooled liquids exhibit spatial heterogeneity in the dynamics of their fluctuating atomic arrangements. The length and time scales of the heterogeneous dynamics are central to the glass transition and influence nucleation and growth of crystals from the liquid. Here, we report direct experimental visualization of the spatially heterogeneous dynamics as a function of temperature in the supercooled liquid state of a Pt-based metallic glass, using electron correlation microscopy with sub-nanometer resolution. An experimental four-point space-time correlation function demonstrates a growing dynamic correlation length, ξ, upon cooling of the liquid toward the glass transition temperature. ξ as a function of the relaxation time τ are in good agreement with Adam-Gibbs theory, inhomogeneous mode-coupling theory and random first-order transition theory of the glass transition. The same experiments demonstrate the existence of a nanometer thickness near-surface layer with order of magnitude shorter relaxation time than inside the bulk.

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confidence: 89%

Spatially heterogeneous dynamics in a metallic glass forming liquid imaged by electron correlation microscopy

et al. 2018

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“…On the basis of eq , the relaxation time τ aging and the Kohlrausch exponent β aging can be obtained (see the solid curve in Figure ). It should be noted that the Kohlrausch exponent β aging is about 0.5 for temperatures close to the glass transition temperature T g based on the experimental results ,,− as well as the simulation techniques by molecular dynamics (MD) . The value of τ determined from the fit of the data during aging is reported in Figure together with the relaxation time obtained from the fit to the isothermal spectra.…”

Section: Resultsmentioning

confidence: 97%

Characteristics of the Structural and Johari–Goldstein Relaxations in Pd-Based Metallic Glass-Forming Liquids

et al. 2014

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The dynamics of Pd-based metallic glass-forming liquids (Pd(40)Ni(10)Cu(30)P(20), Pd(42.5)Ni(7.5)Cu(30)P(20), Pd(40)Ni(40)P(20), and Pd(30)Ni(50)P(20)) was studied by mechanical spectroscopy and modulated differential scanning calorimetry (MDSC). We found that the change in composition has a significant effect on the α relaxation dynamics; the largest difference corresponds to an increase of the glass transition temperature Tg of ∼ 15 K, for materials in which 30% Ni was substituted by 30% Cu (i.e., from Pd(40)Ni(40)P(20) to Pd(40)Ni(10)Cu(30)P(20)). We also found that all Pd-based metallic glasses have very similar fragilities, 59 < m < 67, and Kohlrausch stretched exponents, 0.59 < βKWW < 0.60. It is interesting that the values of m and βKWW correlate well with the general relation proposed by Böhmer et al. for nonmetallic glass formers (Böhmer, R.; et al. J. Chem. Phys. 1993, 99, 4201-4209), which for the observed βKWW values predicts 58 < m < 61. From a linear deconvolution of the α and β relaxations, we find that the substitution of the Ni with Cu induced a large change in the time constant of the Johari-Goldstein relaxation, τβ. The activation energy, Uβ, of the β relaxation was largely independent of chemical composition. In all cases, 25 < Uβ/RT < 28, a range in agreement with results for other glass formers (Kudlik, A.; et al. Europhys. Lett. 1997, 40, 649-654 and Ngai, K. L.; et al. Phys. Rev. E 2004, 69, 031501). From the heat capacity and mechanical loss, estimates were obtained for the number of dynamically correlated units, Nc; we find significantly larger values for these metallic glass-forming liquids than Nc for other glass-forming materials.

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“…Although a vast amount of detailed knowledge on the behaviors of glasses has been accumulated, our understanding of dynamical heterogeneity is still a matter of debate. Initially motivated by explaining the nonexponentiality of relaxation processes in supercooled liquids, two fundamentally different explanations have been put forward: (1) The relaxation process is locally exponential, but the typical relaxation time scale varies spatially; (2) The relaxation process is complicated and inherently nonexponential, and all microscopic regions decay similarly [25][26][27][28][29]. We have investigated the strain clusters induced by the dopant Ni atoms that play an important role in reaching the transition state [30], which is similar to icosahedral in structure glass [31].…”

Section: Introductionmentioning

confidence: 99%

Disorder enhanced dynamical heterogeneity in strain glass alloys

Tao,

Zong

2023

J. Phys.: Condens. Matter

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An open question related to strain-glass (STG) alloys is whether they process similar dynamical behaviors to other glass systems. In the present work, we investigate the reorientation process of martensite domains in both STG and martensitic alloys. Our results show the presence of highly doped point defects can greatly intensify the dynamical heterogeneity and spatiotemporal correlation in ferroelastic or shape memory alloy systems, which are also two main hallmarks of structural glasses. What’s more, we find that such dynamic heterogeneity exists in a different range spanning microscopic to mesoscopic scales, indicated by our molecular dynamic (MD) simulations and time-dependent Ginzburg-Landau (TDGL) modeling. Dopant atoms induced transient strain networks, i.e., spatial correlated local lattice distortion, is a response for such heterogeneous dynamics. The present study thus solidifies strain glass as a new state of matter and may provide guidelines for developing new strain glass alloys.

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Non-exponentiality of structural relaxations in glass forming metallic liquids

Cited by 18 publications

References 77 publications

Spatially heterogeneous dynamics in a metallic glass forming liquid imaged by electron correlation microscopy

Spatially heterogeneous dynamics in a metallic glass forming liquid imaged by electron correlation microscopy

Characteristics of the Structural and Johari–Goldstein Relaxations in Pd-Based Metallic Glass-Forming Liquids

Disorder enhanced dynamical heterogeneity in strain glass alloys

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