High temperature melt viscosity and fragile to strong transition in Zr–Cu–Ni–Al–Nb(Ti) and Cu47Ti34Zr11Ni8 bulk metallic glasses

Evenson, Zach; Schmitt, Tobias; Nicola, Mathias; Gallino, Isabella; Busch, Ralf

doi:10.1016/j.actamat.2012.05.019

Cited by 90 publications

(44 citation statements)

References 44 publications

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“…As shown in Figure 4 and in Tables 1 and 2 The Pd-based, the Pt-based, and the Ni 69 Cr 8.5 Nb 3 P 16.5 B 3 BMG compositions show a distinctively more fragile behavior than the other BMGs in terms of kinetic fragility. As shown in Figure 4 and in Tables 1 and 2, these [41,57]. During undercooling, the Zr-based glass formers undergo a fragile-to-strong transition and the viscosity values measured in the ultra-viscous state in the vicinity of the glass transition are associated with high D* values similar to those of the Mg-based BMGs [20,[33][34][35][36].…”

Section: Fitting Proceduresmentioning

confidence: 59%

On the Fragility of Bulk Metallic Glass Forming Liquids

Gallino

2017

Entropy

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Abstract:In contrast to pure metals and most non-glass forming alloys, metallic glass-formers are moderately strong liquids in terms of fragility. The notion of fragility of an undercooling liquid reflects the sensitivity of the viscosity of the liquid to temperature changes and describes the degree of departure of the liquid kinetics from the Arrhenius equation. In general, the fragility of metallic glass-formers increases with the complexity of the alloy with differences between the alloy families, e.g., Pd-based alloys being more fragile than Zr-based alloys, which are more fragile than Mg-based alloys. Here, experimental data are assessed for 15 bulk metallic glasses-formers including the novel and technologically important systems based on Ni-Cr-Nb-P-B, Fe-Mo-Ni-Cr-P-C-B, and Au-Ag-Pd-Cu-Si. The data for the equilibrium viscosity are analyzed using the Vogel-Fulcher-Tammann (VFT) equation, the Mauro-Yue-Ellison-Gupta-Allan (MYEGA) equation, and the Adam-Gibbs approach based on specific heat capacity data. An overall larger trend of the excess specific heat for the more fragile supercooled liquids is experimentally observed than for the stronger liquids. Moreover, the stronger the glass, the higher the free enthalpy barrier to cooperative rearrangements is, suggesting the same microscopic origin and rigorously connecting the kinetic and thermodynamic aspects of fragility.

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Section: Fitting Proceduresmentioning

confidence: 59%

On the Fragility of Bulk Metallic Glass Forming Liquids

Gallino

2017

Entropy

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“…(11) is calculated to be $5.34. This value sits in between those of two typical Zr-based BMGs, 4.83 [25] for Vitreloy 1 and 6.36 for Vitreloy 106 [44,45]. Since it is reasonable to believe that u ⁄ scales with f, or log (f), the u ⁄ of ZT1 should be between those of Vitreloy 1 (u ⁄ $ 10 lm) [43] and Vitreloy 106 (u ⁄ $ 20 lm) [46].…”

Section: The Paris Regimementioning

confidence: 92%

Fatigue endurance limit and crack growth behavior of a high-toughness Zr61Ti2Cu25Al12 bulk metallic glass

Song

et al. 2015

Acta Materialia

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a b s t r a c tWe report the fatigue damage behavior of a Zr 61 Ti 2 Cu 25 Al 12 (ZT1) bulk metallic glass (BMG), which was known to have a record-high fracture toughness. The ZT1 exhibits the highest fatigue endurance limit among all BMGs, with a normalized fatigue limit of r a = 440 MPa (in four-point bending at a loading ratio of 0.1), or $0.27 of its tensile strength. The crack-growth resistance in the stress/life tests arises from crack-tip plastic shielding due to prolific shear-banding, as well as deflected crack path following a ''zigzag'' pattern. The relation between the range of stress intensity factor (DK) and the crack-growth rate (crack extension per cycle, da/dN) was also determined. ZT1 shows a fatigue threshold, DK th , of 2.8 MPa p m, which appears to be related to the onset of shear band nucleation. Three distinct regimes of fatigue crack growth were observed, with different slopes in the da/dN-DK curve, attributable to different micromechanisms. In the Paris regime, each fatigue striation on fracture surface is generated by a number of loading cycles, rather than by a single loading cycle. In general, the DK th of a BMG approximately scales with its fracture toughness. At different levels of DK, shear bands appear to play different roles, either facilitating or blunting the crack growth.

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“…The properties of the alloy melt were set as typical values of common BMGs prepared by this method. [19][20][21] The simulations were performed in ANSYS using the PLANE77 thermal solid elements. In the water quenching model, the element size was set as 0.5 mm.…”

Section: Simulationmentioning

confidence: 99%

“…12,[19][20][21] T N was selected as ∼0.8T M . Then two series of data of cooling rate R versus diameter D could be obtained.…”

Section: B Evolution Of Cooling Rate With Increasing Sample Sizementioning

confidence: 99%

A study of cooling process in bulk metallic glasses fabrication

et al. 2015

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To study the temperature distribution and evolution during bulk metallic glasses fabrication, finite element method was taken to simulate the cooling process in glassy alloys fabricated by water quenching and copper mold casting. The temperature distribution and evolution in different-sized samples in the two methods were successfully reproduced. The result showed that the temperature distribution in the alloy was strongly affected by fabricating method. Two relations were then proposed to estimate the cooling rate in different-sized samples prepared by these two methods. By comparing the reported data of critical size and critical cooling rate, we showed that the reported critical size and critical cooling rate of metallic glasses didn’t follow a heat transfer relation. Those critical-sized glassy alloys actually experienced cooling rates much larger than the critical cooling rates estimated by the classical nucleation theory or experiments on milligram-scaled samples. It results from the increasing degree of heterogeneity with sample size, and therefore a larger sample requires a faster cooling rate to avoid crystallization. This work clearly shows the temperature field evolution in bulk metallic glasses fabrication and reveals that the critical cooling rate of metallic glasses might be size-dependent.

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High temperature melt viscosity and fragile to strong transition in Zr–Cu–Ni–Al–Nb(Ti) and Cu47Ti34Zr11Ni8 bulk metallic glasses

Cited by 90 publications

References 44 publications

On the Fragility of Bulk Metallic Glass Forming Liquids

On the Fragility of Bulk Metallic Glass Forming Liquids

Fatigue endurance limit and crack growth behavior of a high-toughness Zr61Ti2Cu25Al12 bulk metallic glass

A study of cooling process in bulk metallic glasses fabrication

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