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Ralf Busch - One of the best experts on this subject based on the ideXlab platform.
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the influence of shear rate and Temperature on the viscosity and fragility of the zr41 2ti13 8cu12 5ni10 0be22 5 metallic glass forming liquid
Acta Materialia, 2007Co-Authors: Prashant Wadhwa, Ralf BuschAbstract:Abstract The shear rate and Temperature dependence of the viscosity in the Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic-glass-forming liquid has been measured in the liquid and undercooled liquid state between 907 and 1300 K. After quenching the alloy into a glassy state, the reheated material displays very high viscosity values above the Liquidus Temperature of 1026 K. This liquid alloy is kinetically strong with pronounced shear thinning. With increasing Temperature a transition to a more fragile liquid is observed with a drastic drop in viscosity that is associated with the disappearance of shear thinning. This fragile state is attained above 1225 K. When cooled from this state the strong state is only recovered when the liquid is deeply undercooled below the Liquidus Temperature. The shear thinning and strong to fragile transition is attributed to the destruction of medium- and short-range order in the liquid by mechanical and thermal effects, respectively.
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time scales for viscous flow atomic transport and crystallization in the liquid and supercooled liquid states of zr41 2ti13 8cu12 5ni10 0be22 5
Physical Review Letters, 1999Co-Authors: A Masuhr, Ralf Busch, T A Waniuk, William L JohnsonAbstract:The shear viscosity of liquid Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 has been measured. At the Liquidus Temperature we find an extremely high viscosity of 2.5 Pa s, favoring glass formation. At deep supercooling the time scales for the diffusion of small and medium sized atoms as reported in the literature decouple from the internal relaxation time as probed by our viscosity measurements. Similarly, crystallization from the supercooled liquid state can be described with an effective diffusivity that scales with the viscosity at high Temperatures and is Arrhenius-like at deep supercooling.
William L Johnson - One of the best experts on this subject based on the ideXlab platform.
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highly processable bulk metallic glass forming alloys in the pt co ni cu p system
Applied Physics Letters, 2004Co-Authors: Jan Schroers, William L JohnsonAbstract:Highly processable bulk metallic glass alloys in the Pt–Co–Ni–Cu–P system were discovered. The alloys show low Liquidus Temperature below 900 K, excellent processability with low critical cooling rate reflecting in maximum casting thicknesses in quartz tubes of up to 20 mm, and a large supercooled liquid region. The Pt57.5Cu14.7Ni5.3P22.5 composition has a Liquidus Temperature of 795 K, a glass transition Temperature of 508 K with a supercooled liquid region of 98 K. For medical and jewelry applications a Ni-free alloy, Pt60Cu16Co2P22 was discovered with a Liquidus Temperature of 881 K, a glass transition Temperature of 506 K, and a supercooled liquid region of 63 K. Glass formation was observed in a wider composition range. Vickers hardness of these alloys is in the 400 Hv range. The alloys can be processed in the supercooled liquid region in air without any measurable oxidation. In this region, a large processing window is available in which the material does not embrittle. Embrittlement in these alloys is correlated with crystallization. It can be avoided as long as substantial crystallization does not take place during isothermal processing in the supercooled liquid region. Also, liquid processing can be performed in air when flux with B2O3.
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Amorphous metallic foam
Applied Physics Letters, 2003Co-Authors: Jan Schroers, Chris Veazey, William L JohnsonAbstract:The bulk glass forming alloy Pd43Ni10Cu27P20 is processed into a low-density amorphous metallic foam. Pd43Ni10Cu27P20 is mixed with hydrated B2O3, which releases gas at elevated Temperature and/or low pressure. Very homogeneous foams are achieved due to the high viscosity of the alloy even at its Liquidus Temperature. By processing at the Liquidus Temperature and decreasing the pressure to 10^–2 mbar, well-distributed bubbles expand to foam the material. Foam densities as low as 1.4×10^3 kg/m^3 were obtained, corresponding to a bubble volume fraction of 84%. The bubble diameter ranges between 2×10^–4 and 1×10^–3 m. Thermal analysis by differential scanning calorimetry confirms the amorphous nature of the foam. Furthermore, it reveals that the foam's thermal stability is comparable to the bulk material.
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time scales for viscous flow atomic transport and crystallization in the liquid and supercooled liquid states of zr41 2ti13 8cu12 5ni10 0be22 5
Physical Review Letters, 1999Co-Authors: A Masuhr, Ralf Busch, T A Waniuk, William L JohnsonAbstract:The shear viscosity of liquid Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 has been measured. At the Liquidus Temperature we find an extremely high viscosity of 2.5 Pa s, favoring glass formation. At deep supercooling the time scales for the diffusion of small and medium sized atoms as reported in the literature decouple from the internal relaxation time as probed by our viscosity measurements. Similarly, crystallization from the supercooled liquid state can be described with an effective diffusivity that scales with the viscosity at high Temperatures and is Arrhenius-like at deep supercooling.
Akihisa Inoue - One of the best experts on this subject based on the ideXlab platform.
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evaluation of glass forming ability of binary metallic glasses with Liquidus Temperature crystallographic data from binary phase diagrams and molecular dynamics simulations
Journal of Alloys and Compounds, 2009Co-Authors: Akira Takeuchi, Kunio Yubuta, Akihiro Makino, Akihisa InoueAbstract:Abstract The glass-forming ability (GFA) of binary metallic glasses was analyzed with data for the Liquidus Temperature ( T l ) acquired as a function of composition from binary phase diagrams, assisted by crystallographic data combined with amorphous-forming composition range (AFCR) and molecular dynamics (MD) simulations. A necessary condition for the formation of bulk metallic glasses (BMGs) was determined as Δ T l ≥ 300 K where Δ T l was defined as a decrease in T l due to eutectic reaction. The crystalline compounds with structure types of bcc or its derivative type, such as CsCl (B2), CrB (B f ), Al 2 Cu (C16) and MoSi 2 (C11 b ), tended to be found in AFCR frequently. The total pair-distribution and interference functions revealed a high forming tendency of a noncrystalline Cu 10 Zr 7 structure created by MD. Simultaneous achievements of the Cu 10 Zr 7 structure for crystallographic features resulting from the bcc family structure and geometrical features in phase diagram for T l affect the formation of Cu 61.8 Zr 38.2 BMG.
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ni free zr fe al cu bulk metallic glasses with high glass forming ability
Scripta Materialia, 2009Co-Authors: Qingsheng Zhang, Wei Zhang, Akihisa InoueAbstract:We report a series of Ni-free quaternary Zr-based bulk metallic glasses developed by substitution of Fe for Cu in ternary Zr 60 Cu 30 Al 10 alloy. Addition of Fe lowers the Liquidus Temperature of the ternary Zr 60 Cu 30 Al 10 alloy. The alloy compositions of Zr 60 Cu 25 Fe 5 Al 10 and Zr 62.5 Cu 22.5 Fe 5 Al 10 were found to be very near a quaternary eutectic point with low Liquidus Temperature. The as-cast glassy alloy rods with a diameter of 20 mm were easily synthesized at Zr 60 Cu 25 Fe 5 Al 10 and Zr 62.5 Cu 22.5 Fe 5 Al 10 alloy compositions by copper mold casting.
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bulk glassy alloys with low Liquidus Temperature in pt cu p system
Materials Transactions, 2003Co-Authors: Tao Zhang, Akihisa InoueAbstract:Bulk glassy alloys with low values of Liquidus Temperature (T 1 ) and glass transition Temperature (Tg) as well as high T g /T 1 were formed at Pt 60 Cu 20 P 20 . Glassy alloys in Pt 80-x Cu x P 20 system were formed over the whole composition range up to 35 at%Cu examined in the present study. The T g increases significantly with increasing Cu content, shows a maximum value of 522 K at 20%Cu and then decreases slightly with further increase in Cu content. On the other hand, the crystallization Temperature (T x ) increases monotonously with increasing Cu content up to 25 at%Cu and then becomes saturated, leading to a monotonous increase in ΔT x (=T x -T g ) from 25 K at 0%Cu to 83 K at 35 at%Cu. All the ternary glassy alloys crystallize through a single-stage exothermic reaction, accompanied by the precipitation of mixed Pt 5 P 2 , Cu 3 P and unknown phases. The 20%Cu-containing alloy has the lowest T 1 of 854 K as well as the smallest Temperature interval of 21 K between T 1 and melting Temperature (T m ) and hence the highest T g /T 1 of 0.61 is obtained for the 20%Cu alloy. The high T g /T 1 as well as the low T 1 has enabled us to form bulk glassy alloy rods with diameters up to at least 12 mm by water quenching. The synthesis of the Pt-Cu-P glassy alloys with the low values of T g and T 1 and the large ΔT x is important for future development as precision materials for nano-technology which can be deformed through viscous flow.
Franz Faupel - One of the best experts on this subject based on the ideXlab platform.
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atomic dynamics in zr based glass forming alloys near the Liquidus Temperature
Physical Review B, 2017Co-Authors: Sri Wahyuni Basuki, Fan Yang, Elisabeth Gill, Klaus Ratzke, A Meyer, Franz FaupelAbstract:We report simultaneous radiotracer diffusion experiments of Co-57 and of Zr-95 in binary $\mathrm{Z}{\mathrm{r}}_{64}\mathrm{N}{\mathrm{i}}_{36}, \mathrm{Z}{\mathrm{r}}_{36}\mathrm{N}{\mathrm{i}}_{64}$, and ternary $\mathrm{Z}{\mathrm{r}}_{60}\mathrm{N}{\mathrm{i}}_{25}\mathrm{A}{\mathrm{l}}_{15}$ alloys above but near the Liquidus Temperature (${T}_{l}$). In contrast to the multicomponent $\mathrm{Z}{\mathrm{r}}_{46.75}\mathrm{T}{\mathrm{i}}_{8.25}\mathrm{C}{\mathrm{u}}_{7.5}\mathrm{N}{\mathrm{i}}_{10}\mathrm{B}{\mathrm{e}}_{27.5}$ (Vit4), where a significant component decoupling at the ${T}_{l}$ is observed, the ratio between Zr and Co self-diffusion coefficients is smaller than two in the alloys with fewer components. The difference in the degree of decoupling compared to Vit4 can be explained in terms of different ${T}_{l}$'s. Moreover, owing to the high accuracy of the simultaneous tracer diffusion technique, we are able to resolve a small but notable composition dependence of the ratio ${D}_{\mathrm{Co}}/{D}_{\mathrm{Zr}}$, which decreases with increasing Zr content for all glass forming alloys reported here. In contrast to a hard sphere (HS)-like mixture, where decoupling is controlled only by atomic sizes, this indicates a coupling of the Co/Ni and Zr diffusion, due to the strong chemical affinity between the diffusing components. Our results are in very good agreement with recent simulations in $\mathrm{Z}{\mathrm{r}}_{64}\mathrm{N}{\mathrm{i}}_{36}$ based on mode coupling theory (MCT).
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decoupling of component diffusion in a glass forming zr 46 75 ti 8 25 cu 7 5 ni 10 be 27 5 melt far above the Liquidus Temperature
Physical Review Letters, 2014Co-Authors: Sri Wahyuni Basuki, Fan Yang, Klaus Ratzke, A Bartsch, Andreas Meyer, Franz FaupelAbstract:We report (95)Zr and (57)Co radiotracer diffusivities and viscosity data in the equilibrium liquid state of a bulk metallic glass forming Zr(46.75)Ti(8.25)Cu(7.5)Ni(10)Be(27.5) melt (Vitreloy 4) far above the Liquidus Temperature T(l) that are not affected by convection, as evidenced via quasielastic neutron scattering. Zr diffusion is strongly decoupled from diffusion of the smaller components by more than a factor of 4 at T(l), although it obeys the Stokes-Einstein equation. The results suggest that, in the present Zr-based metallic glass forming systems, diffusion and viscous flow start to develop solidlike, i.e., energy-landscape-controlled, features already in the stable liquid state more than 300 K above the mode coupling Temperature T(c).
Lingxue Kong - One of the best experts on this subject based on the ideXlab platform.
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effect of cao fe2o3 ratio on fusibility of coal ashes with high silica and alumina levels and prediction
Fuel, 2020Co-Authors: Wenju Shi, Lingxue Kong, Jin Bai, Zongqing Bai, Stefan Guhl, Huiling Zhao, Bernd MeyerAbstract:Abstract Ash fusibility which is usually investigated and evaluated by the ash chemical compositions is widely used to guide the coal selection in boiler and gasifier. Calcium and iron are the main basic oxides in coal ash, which tend to decrease ash fusion Temperatures (AFTs). However, the change of AFTs varied with CaO/Fe2O3 mass ratio is not yet revealed. In this work, effect of CaO/Fe2O3 ratio on the fusibility of ash with high silica and alumina levels was explored under weak reducing atmosphere (CO: CO2 = 3/2, volume ratio). Thermodynamic calculations were applied to investigate the fusion behavior. A general rise of AFTs with the increasing CaO/Fe2O3 ratio was verified, especially for the coal ash with low SiO2 + Al2O3 level and SiO2/Al2O3 mass ratio. Mullite and anorthite are main refractory minerals phase of the ash samples with high SiO2 and Al2O3 levels. The fusion of the ash in anorthite primary phase is the “soft-melting” mechanism, and Liquidus Temperature was well used to predict flow Temperature (FT). However, the Liquidus Temperature should not be used to predict FT of the ash in mullite primary phase due to the “melting-dissolve” mechanism. A Tmullite model was proposed to predict FT for the ashes in mullite primary phase. The deviation of predicted and measured FT was within the measuring error range (±40 °C), which was supported by 25 real coal ashes.
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a new method of estimating the Liquidus Temperature of coal ash slag using ash composition
Chemical Engineering Science, 2018Co-Authors: Lingxue Kong, Xiaoming Li, Jiang Xu, Wen LiAbstract:Abstract The Liquidus Temperature (Tliq) of coal ash is above the Temperature at which the last solid phase disappeared. Tliq of coal ash slag is widely used to evaluate ash fusion and flow behaviors. The method of determining the Liquidus Temperature is based on phase equilibrium, the activation energy of viscous flow and chemical composition models. In this work, a linear relation between average molar ionic potential (Ia) and potential energy (Pe) as well as Tliq and potential energy is supported by molecular dynamics simulations. We correlated Tliq (derived from thermodynamic equilibrium calculation) and the molar ionic potential of the chemical composition. The linear relation between coal ash composition and the Tliq is established for the first time, with T liq = ( 170.43 - 3.1457 × I a ) × S / A + 15.725 × I a + 360.78 (DE
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Effects of CaCO3 on slag flow properties at high Temperatures
Fuel, 2013Co-Authors: Lingxue Kong, Jin Bai, Zongqing Bai, Zhenxing GuoAbstract:Abstract Experiments were conducted on the selected ashes with different additions of CaCO 3 for understanding the effects on slag flow properties including ash fusion Temperatures, slag viscosity, Temperature of critical viscosity and type of slag. ICP-AES, XRD and FTIR analyses were applied to determine the component and structure of the slags. Factsage was used to calculate Liquidus Temperatures in the SiO 2 –Al 2 O 3 –CaO–FeO system and to predict formed mineral matters and proportion of solid phase as a function of Temperatures. The results show that the Liquidus Temperature calculated by Factsage well predicts the variation of ash fusion Temperatures. Slag viscosity behavior changes with increasing addition of CaCO 3 because the formation process of solid phase is different. The Fourier transform infrared (FTIR) spectrum indicates that Ca 2+ leads to break polymerized Si–O–Si into Si–O, so the increasing Ca 2+ in slag results in the decrease of viscosity above Liquidus Temperature. Below Liquidus Temperature, solids content decreases with increasing addition of CaCO 3 above the Temperature of critical viscosity ( T cv ). Meanwhile, it is found that the rate of solid formation is related with T cv and a new prediction method of T cv based on that was proposed. Moreover, the type of slag changed with addition of CaCO 3 was predictable by XRD analysis. The prediction on ash fusion Temperature, T cv and type of slag is expected to serve as a reference for adding flux to regulate coal/ash properties suitable for slag tapping gasification technology.