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L. Zhou - One of the best experts on this subject based on the ideXlab platform.
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the nanocrystal and its thermal stability in ti40zr25ni8cu9be18 metallic glass during Homogeneous Deformation
Materials Science Forum, 2011Co-Authors: X Zhou, Hongchao Kou, Junbiao Wang, L. ZhouAbstract:For Ti40Zr25Ni8Cu9Be18 metallic glass, nanocrystal forms in the as-cast amorphous matrix during fast cooling from supercooled liquid, and precipitates from amorphous matrix during heating process. The thermal stability of the nanocrystals during Homogeneous temperature is influenced by Deformation temperature. At relative low Deformation temperature (below Tx-40K), the nanocrystal is very stable. Contrarily, nanocrystal exhibits low thermal stability at relative high Deformation temperature (above Tx-40K). Moreover, nanocrystal precipitated during heating process possesses better thermal stability than nanocrystal existed in as cast condition at the same Deformation temperature.
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Homogeneous Deformation of Ti41.5Cu37.5Ni7.5Zr2.5Hf5Si1 bulk metallic glass in the supercooled liquid region
Intermetallics, 2011Co-Authors: J.n. Mei, Jean-louis Soubeyroux, Jean-jacques Blandin, H.c. Kou, L. ZhouAbstract:The Homogeneous Deformation behavior of Ti41.5Cu37.5Ni7.5Zr2.5Hf5Sn5Si1 BMG has been investigated by compression tests. The results show that its high-temperature Deformation behavior is strongly dependent on strain rate and temperature, and there exists a transition from non-Newtonian flow to Newtonian flow with decrease in strain rate, which can be explained based on the transition state theory. In addition, this alloy can reach a large compressive strain than 0.8 at high strain rate; however the much higher flow stress and lower value of S parameter compared with typical BMGs indicates its worse formability in the SLR. A beneficial domain (temperature and strain rate) for optimum hot workability of this alloy has been roughly located by constructing the power dissipation efficiency map, where the power dissipation efficiency is larger than 0.8.
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Homogeneous Deformation of ti41 5cu37 5ni7 5zr2 5hf5sn5si1 bulk metallic glass in the supercooled liquid region
Intermetallics, 2011Co-Authors: J.n. Mei, Jean-louis Soubeyroux, Jean-jacques Blandin, Hongchao Kou, L. ZhouAbstract:The Homogeneous Deformation behavior of Ti41.5Cu37.5Ni7.5Zr2.5Hf5Sn5Si1 BMG has been investigated by compression tests. The results show that its high-temperature Deformation behavior is strongly dependent on strain rate and temperature, and there exists a transition from non-Newtonian flow to Newtonian flow with decrease in strain rate, which can be explained based on the transition state theory. In addition, this alloy can reach a large compressive strain than 0.8 at high strain rate; however the much higher flow stress and lower value of S parameter compared with typical BMGs indicates its worse formability in the SLR. A beneficial domain (temperature and strain rate) for optimum hot workability of this alloy has been roughly located by constructing the power dissipation efficiency map, where the power dissipation efficiency is larger than 0.8.
J.n. Mei - One of the best experts on this subject based on the ideXlab platform.
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Homogeneous Deformation of Ti41.5Cu37.5Ni7.5Zr2.5Hf5Si1 bulk metallic glass in the supercooled liquid region
Intermetallics, 2011Co-Authors: J.n. Mei, Jean-louis Soubeyroux, Jean-jacques Blandin, H.c. Kou, L. ZhouAbstract:The Homogeneous Deformation behavior of Ti41.5Cu37.5Ni7.5Zr2.5Hf5Sn5Si1 BMG has been investigated by compression tests. The results show that its high-temperature Deformation behavior is strongly dependent on strain rate and temperature, and there exists a transition from non-Newtonian flow to Newtonian flow with decrease in strain rate, which can be explained based on the transition state theory. In addition, this alloy can reach a large compressive strain than 0.8 at high strain rate; however the much higher flow stress and lower value of S parameter compared with typical BMGs indicates its worse formability in the SLR. A beneficial domain (temperature and strain rate) for optimum hot workability of this alloy has been roughly located by constructing the power dissipation efficiency map, where the power dissipation efficiency is larger than 0.8.
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Homogeneous Deformation of ti41 5cu37 5ni7 5zr2 5hf5sn5si1 bulk metallic glass in the supercooled liquid region
Intermetallics, 2011Co-Authors: J.n. Mei, Jean-louis Soubeyroux, Jean-jacques Blandin, Hongchao Kou, L. ZhouAbstract:The Homogeneous Deformation behavior of Ti41.5Cu37.5Ni7.5Zr2.5Hf5Sn5Si1 BMG has been investigated by compression tests. The results show that its high-temperature Deformation behavior is strongly dependent on strain rate and temperature, and there exists a transition from non-Newtonian flow to Newtonian flow with decrease in strain rate, which can be explained based on the transition state theory. In addition, this alloy can reach a large compressive strain than 0.8 at high strain rate; however the much higher flow stress and lower value of S parameter compared with typical BMGs indicates its worse formability in the SLR. A beneficial domain (temperature and strain rate) for optimum hot workability of this alloy has been roughly located by constructing the power dissipation efficiency map, where the power dissipation efficiency is larger than 0.8.
Tsuyoshi Masumoto - One of the best experts on this subject based on the ideXlab platform.
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Deformation behavior of zr65al10ni10cu15 glassy alloy with wide supercooled liquid region
Applied Physics Letters, 1996Co-Authors: Yoshihito Kawamura, Tsutomu Shibata, Akihisa Inoue, Tsuyoshi MasumotoAbstract:We report the stress‐strain behavior for a Zr65Al10Ni10Cu15 (at.%) glassy alloy with a significant supercooled liquid region of 105 K. The transition temperature from inHomogeneous Deformation to a Homogeneous one increases with increasing strain rate. The alloy in the supercooled liquid state, however, exhibited the Homogeneous Deformation even at higher strain rates above 0.5 s−1. The strength was also dependent on the strain rate and independent of temperature in the inHomogeneous Deformation region, and was sensitive to both strain rate and temperature in the Homogeneous region. The stress‐strain curves in the Homogeneous Deformation mode were accompanied by a stress overshoot and its height increases with increasing temperature and strain rate.
T G Nieh - One of the best experts on this subject based on the ideXlab platform.
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inHomogeneous to Homogeneous transition in an au based metallic glass and its Deformation maps
Intermetallics, 2010Co-Authors: S X Song, J C Huang, J S C Jang, T G NiehAbstract:Abstract Transition from inHomogeneous to Homogeneous Deformation was characterized in an Au 49 Ag 5.5 Pd 2.3 Cu 26.9 Si 16.3 metallic glass by compression of micro-scaled pillar samples and morphological observations of deformed specimens. In compression, the transition was revealed as the absence of flow serration in a stress–strain curve. Morphologically, it corresponds to the disappearance of localized shear band and the sample is uniformly deformed. The transition was found to be both temperature and strain rate dependent, and at a higher strain rate, it occurred at a higher temperature. The Homogeneous Deformation and, in particular the stress overshoot phenomenon, could be described by a shear transition zone model. Based on the current data, Deformation maps were developed for the Au 49 Ag 5.5 Pd 2.3 Cu 26.9 Si 16.3 metallic glass.
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Homogeneous Deformation of au based metallic glass micropillars in compression at elevated temperatures
Applied Physics Letters, 2009Co-Authors: S X Song, Y H Lai, J C Huang, T G NiehAbstract:We performed high-temperature microcompression tests on micron-sized pillar samples fabricated from Au49Ag5.5Pd2.3Cu26.9Si16.3 metallic glass near the glass transition temperature to investigate the Homogeneous Deformation behavior. Samples were invariably deformed uniformly. The strength was observed to decrease with increasing temperature and decreasing strain rate. Plastic flow behavior can be described by a shear transition zone model. The activation energy and the size of the basic flow unit were both deduced and compared favorably with the theory.
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Homogeneous Deformation of bulk metallic glasses
Scripta Materialia, 2006Co-Authors: T G Nieh, J WadsworthAbstract:Abstract Homogeneous Deformation of bulk metallic glasses (BMGs) is reviewed. Homogeneous Deformation usually takes place at temperatures near and above the glass transition temperature. The Deformation behavior depends upon strain rate. At low strain rates, BMGs behave like a Newtonian fluid (m = 1) but plastic flow becomes non-Newtonian at high strain rates. The non-Newtonian behavior is a result of microstructural instability, namely, the concurrent formation of nanocrystals in the amorphous matrix during Deformation. Despite the difference in Deformation behavior, BMGs usually show large ductility (over 300%) at temperatures in the supercooled liquid region.
J L Soubeyroux - One of the best experts on this subject based on the ideXlab platform.
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Homogeneous Deformation of bulk metallic glasses in the super cooled liquid state
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: M Bletry, Pierre Guyot, Y Brechet, J J Blandin, J L SoubeyrouxAbstract:Abstract Different Zr–Ti–Al–Ni–Cu bulk metallic glasses have been processed. They have been characterized by neutron and X-ray diffraction in the glassy state and after DSC heating up to crystallization. The Homogeneous visco-plasticity of the glasses has been studied in the under-cooled liquid state by compression tests at constant strain-rate and by differential mechanical tests with strain-rate jumps at different temperatures. The flow stress appears to be strongly thermally activated. Another characteristic feature of the Deformation of the fully amorphous state is that the flow stress is independent of the strain-rate path followed to reach a given level of strain. The stress–strain curves and their dependence on temperature and strain-rate are then discussed in terms of Newtonian and non-Newtonian viscosity. It is shown that a reduced viscosity can be scaled on a master curve, independently of the strain-rate and temperature. A second analysis of the results is made, in terms of free volume. The temperature and stress variation of the plastic flow are compared with Spaepen model. A constitutive equation of the Deformation is proposed. Finally, the effect of crystallization on mechanical behaviour of metallic glasses is treated trough a model involving backstress due to a composite behaviour.
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Homogeneous Deformation of zr ti al cu ni bulk metallic glasses
Intermetallics, 2004Co-Authors: M Bletry, Pierre Guyot, Y Brechet, J J Blandin, J L SoubeyrouxAbstract:Abstract Zr–Ti–Al–Ni–Cu bulk metallic glasses have been prepared by copper mould casting and were characterized using neutron and X-ray diffraction and scanning calorimetry in the as-cast glassy state and during crystallization. Depending on chemical composition, the under-cooled liquid domain separating the glass transition temperature (Tg) from the onset of crystallization (Tx) ranges from 82 to 102 K, for a heating rate of 20 K/min. The visco-plastic behaviour of the material has been studied in the supercooled liquid state, between Tg and Tx, using constant strain-rate compression tests and strain-rate jump tests. The stress–strain curves display an overshoot at large strain-rate and low temperatures, followed by a constant flow stress up to very large plastic strains. The flow stress is strongly thermally activated. Another characteristic feature of the Deformation of the fully amorphous state is the independence of the flow stress on the strain-rate path. The stress–strain curves and their dependence on temperature and strain-rate are first discussed in terms of glass viscosity. It is shown that the data obtained at various temperatures and strain-rates can be scaled on a master curve. The master curve is directly deduced from the stationary strain-rate proposed by Spaepen for Homogeneous flow based on the free volume concept. Deformation constitutive laws are then established in the out of equilibrium general case, taking into account the strain induced free volume creation and relaxation. They allow an accurate description of the transients regimes commonly observed such as overshoot, stress oscillations and strain-rate changes. Finally, the hardening resulting from partial crystallization is described by the introduction of a back-stress originating in the undeformability of the crystallites.