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Masakazu Tane - One of the best experts on this subject based on the ideXlab platform.

  • elastic modulus enhancement during room temperature aging and its suppression in metastable ti nb based alloys with low body centered Cubic phase stability
    Acta Materialia, 2016
    Co-Authors: Masakazu Tane, Takayoshi Nakano, Koji Hagihara, Masato Ueda, Yosiyuki Okuda
    Abstract:

    Abstract Changes in the elastic properties during room-temperature aging (RT aging) of metastable Ti–Nb-based alloy single crystals with low Body-Centered Cubic (bcc)-phase stability were investigated. The elastic stiffness components of Ti–Nb–Ta–Zr alloys with different Nb concentrations were measured by resonant ultrasound spectroscopy during RT aging; the results revealed that shear moduli c ′ and c 44 were increased by RT aging. In the alloy with the lowest Nb concentration, i.e., with the lowest bcc phase stability, shear moduli c ′ and c 44 were enhanced by the largest amount. The increase rates were ∼5% for 1.1 × 10 7  s (127 days), whereas the bulk modulus was hardly changed by aging. In Ti–Nb–Ta–Zr–O alloys with different oxygen concentrations, shear moduli c ′ and c 44 of the alloy with the lowest oxygen concentration increased most significantly. Moreover, the electrical resistivity of Ti–Nb–Ta–Zr and Ti–Nb–Ta–Zr–O alloys was increased by RT aging. Importantly, the enhancements of shear moduli and electrical resistivity were suppressed by increases in the bcc-phase stability (i.e., increase in the Nb concentration) and oxygen concentration; these factors are known to suppress ω (hexagonal) phase formation. However, transmission electron microscopy (TEM) observations revealed that only a diffuse ω structure—an ω -like lattice distortion—was formed after RT aging. On the basis of alloying element effects, TEM observations, and analysis of the changes in elastic properties by using a micromechanics model, it was deduced that the enhancements of shear moduli and electrical resistivity were possibly caused by the formation of a diffuse ω structure.

  • ω transformation in cold worked ti nb ta zr o alloys with low body centered Cubic phase stability and its correlation with their elastic properties
    Acta Materialia, 2013
    Co-Authors: Masakazu Tane, Takayoshi Nakano, Mitsuo Niinomi, Shigeru Kuramoto, Naohisa Takesue, Hideo Nakajima
    Abstract:

    Abstract The ω transformation and its correlation with elastic properties were investigated in cold-worked Ti–36Nb–2Ta–3Zr– x O mass% alloys with low Body-Centered Cubic ( β ) phase stability, known as gum metal. Analysis of the temperature dependence of the ω (hexagonal) phase formation using transmission electron microscopy and of the elastic properties of solution-treated and cold-worked alloys using resonant ultrasound spectroscopy revealed that in the solution-treated 0.36% and 0.51% O alloys, the high concentration of oxygen suppressed ω -phase formation from room temperature to a fairly low temperature of ∼13 K. However, the ω phase was formed by cold working at room temperature in the 0.30% and 0.47% O alloys. Importantly, the fraction of the ω phase clearly increased upon cooling, which indicates that the formation of the ω phase is thermodynamically favorable near and below room temperature in the cold-worked 0.30% and 0.47% O alloys. This formation of the ω phase and the low stability of the β phase related to the low electron/atom ( e / a ) ratio were the dominant factors determining the elastic properties near and below room temperature in the cold-worked Ti–Nb–Ta–Zr–O alloys.

  • low young s modulus of ti nb ta zr alloys caused by softening in shear moduli c and c44 near lower limit of body centered Cubic phase stability
    Acta Materialia, 2010
    Co-Authors: Masakazu Tane, S Akita, Takayoshi Nakano, Koji Hagihara, Yukichi Umakoshi, Mitsuo Niinomi, Hirotaro Mori, Hideo Nakajima
    Abstract:

    Abstract The composition and temperature dependence of the elastic properties and phase stability of quaternary Ti–Nb–Ta–Zr β-phase alloys with a Body-Centered Cubic structure, developed for biomedical applications, were investigated using their single crystals, in order to clarify the origin of the low Young’s modulus in polycrystals. Transmission electron microscopy observations clarified that α ″ martensitic transformation occurred in a temperature range that depended on the β-phase stability below room temperature. Electromagnetic acoustic resonance measurements clarified that the shear moduli c ′ and c 44 of single crystals softened upon cooling from room temperature and became rather low near the martensitic transformation start temperature, i.e. the lower limit of β-phase stability. An analysis by the Hill approximation indicates that low c ′ and c 44 caused the low Young’s modulus, and thus it is probable that the softening in c ′ and c 44 is the origin of the low Young’s modulus.

Hideo Nakajima - One of the best experts on this subject based on the ideXlab platform.

  • ω transformation in cold worked ti nb ta zr o alloys with low body centered Cubic phase stability and its correlation with their elastic properties
    Acta Materialia, 2013
    Co-Authors: Masakazu Tane, Takayoshi Nakano, Mitsuo Niinomi, Shigeru Kuramoto, Naohisa Takesue, Hideo Nakajima
    Abstract:

    Abstract The ω transformation and its correlation with elastic properties were investigated in cold-worked Ti–36Nb–2Ta–3Zr– x O mass% alloys with low Body-Centered Cubic ( β ) phase stability, known as gum metal. Analysis of the temperature dependence of the ω (hexagonal) phase formation using transmission electron microscopy and of the elastic properties of solution-treated and cold-worked alloys using resonant ultrasound spectroscopy revealed that in the solution-treated 0.36% and 0.51% O alloys, the high concentration of oxygen suppressed ω -phase formation from room temperature to a fairly low temperature of ∼13 K. However, the ω phase was formed by cold working at room temperature in the 0.30% and 0.47% O alloys. Importantly, the fraction of the ω phase clearly increased upon cooling, which indicates that the formation of the ω phase is thermodynamically favorable near and below room temperature in the cold-worked 0.30% and 0.47% O alloys. This formation of the ω phase and the low stability of the β phase related to the low electron/atom ( e / a ) ratio were the dominant factors determining the elastic properties near and below room temperature in the cold-worked Ti–Nb–Ta–Zr–O alloys.

  • low young s modulus of ti nb ta zr alloys caused by softening in shear moduli c and c44 near lower limit of body centered Cubic phase stability
    Acta Materialia, 2010
    Co-Authors: Masakazu Tane, S Akita, Takayoshi Nakano, Koji Hagihara, Yukichi Umakoshi, Mitsuo Niinomi, Hirotaro Mori, Hideo Nakajima
    Abstract:

    Abstract The composition and temperature dependence of the elastic properties and phase stability of quaternary Ti–Nb–Ta–Zr β-phase alloys with a Body-Centered Cubic structure, developed for biomedical applications, were investigated using their single crystals, in order to clarify the origin of the low Young’s modulus in polycrystals. Transmission electron microscopy observations clarified that α ″ martensitic transformation occurred in a temperature range that depended on the β-phase stability below room temperature. Electromagnetic acoustic resonance measurements clarified that the shear moduli c ′ and c 44 of single crystals softened upon cooling from room temperature and became rather low near the martensitic transformation start temperature, i.e. the lower limit of β-phase stability. An analysis by the Hill approximation indicates that low c ′ and c 44 caused the low Young’s modulus, and thus it is probable that the softening in c ′ and c 44 is the origin of the low Young’s modulus.

Takayoshi Nakano - One of the best experts on this subject based on the ideXlab platform.

  • elastic modulus enhancement during room temperature aging and its suppression in metastable ti nb based alloys with low body centered Cubic phase stability
    Acta Materialia, 2016
    Co-Authors: Masakazu Tane, Takayoshi Nakano, Koji Hagihara, Masato Ueda, Yosiyuki Okuda
    Abstract:

    Abstract Changes in the elastic properties during room-temperature aging (RT aging) of metastable Ti–Nb-based alloy single crystals with low Body-Centered Cubic (bcc)-phase stability were investigated. The elastic stiffness components of Ti–Nb–Ta–Zr alloys with different Nb concentrations were measured by resonant ultrasound spectroscopy during RT aging; the results revealed that shear moduli c ′ and c 44 were increased by RT aging. In the alloy with the lowest Nb concentration, i.e., with the lowest bcc phase stability, shear moduli c ′ and c 44 were enhanced by the largest amount. The increase rates were ∼5% for 1.1 × 10 7  s (127 days), whereas the bulk modulus was hardly changed by aging. In Ti–Nb–Ta–Zr–O alloys with different oxygen concentrations, shear moduli c ′ and c 44 of the alloy with the lowest oxygen concentration increased most significantly. Moreover, the electrical resistivity of Ti–Nb–Ta–Zr and Ti–Nb–Ta–Zr–O alloys was increased by RT aging. Importantly, the enhancements of shear moduli and electrical resistivity were suppressed by increases in the bcc-phase stability (i.e., increase in the Nb concentration) and oxygen concentration; these factors are known to suppress ω (hexagonal) phase formation. However, transmission electron microscopy (TEM) observations revealed that only a diffuse ω structure—an ω -like lattice distortion—was formed after RT aging. On the basis of alloying element effects, TEM observations, and analysis of the changes in elastic properties by using a micromechanics model, it was deduced that the enhancements of shear moduli and electrical resistivity were possibly caused by the formation of a diffuse ω structure.

  • ω transformation in cold worked ti nb ta zr o alloys with low body centered Cubic phase stability and its correlation with their elastic properties
    Acta Materialia, 2013
    Co-Authors: Masakazu Tane, Takayoshi Nakano, Mitsuo Niinomi, Shigeru Kuramoto, Naohisa Takesue, Hideo Nakajima
    Abstract:

    Abstract The ω transformation and its correlation with elastic properties were investigated in cold-worked Ti–36Nb–2Ta–3Zr– x O mass% alloys with low Body-Centered Cubic ( β ) phase stability, known as gum metal. Analysis of the temperature dependence of the ω (hexagonal) phase formation using transmission electron microscopy and of the elastic properties of solution-treated and cold-worked alloys using resonant ultrasound spectroscopy revealed that in the solution-treated 0.36% and 0.51% O alloys, the high concentration of oxygen suppressed ω -phase formation from room temperature to a fairly low temperature of ∼13 K. However, the ω phase was formed by cold working at room temperature in the 0.30% and 0.47% O alloys. Importantly, the fraction of the ω phase clearly increased upon cooling, which indicates that the formation of the ω phase is thermodynamically favorable near and below room temperature in the cold-worked 0.30% and 0.47% O alloys. This formation of the ω phase and the low stability of the β phase related to the low electron/atom ( e / a ) ratio were the dominant factors determining the elastic properties near and below room temperature in the cold-worked Ti–Nb–Ta–Zr–O alloys.

  • low young s modulus of ti nb ta zr alloys caused by softening in shear moduli c and c44 near lower limit of body centered Cubic phase stability
    Acta Materialia, 2010
    Co-Authors: Masakazu Tane, S Akita, Takayoshi Nakano, Koji Hagihara, Yukichi Umakoshi, Mitsuo Niinomi, Hirotaro Mori, Hideo Nakajima
    Abstract:

    Abstract The composition and temperature dependence of the elastic properties and phase stability of quaternary Ti–Nb–Ta–Zr β-phase alloys with a Body-Centered Cubic structure, developed for biomedical applications, were investigated using their single crystals, in order to clarify the origin of the low Young’s modulus in polycrystals. Transmission electron microscopy observations clarified that α ″ martensitic transformation occurred in a temperature range that depended on the β-phase stability below room temperature. Electromagnetic acoustic resonance measurements clarified that the shear moduli c ′ and c 44 of single crystals softened upon cooling from room temperature and became rather low near the martensitic transformation start temperature, i.e. the lower limit of β-phase stability. An analysis by the Hill approximation indicates that low c ′ and c 44 caused the low Young’s modulus, and thus it is probable that the softening in c ′ and c 44 is the origin of the low Young’s modulus.

Levente Vitos - One of the best experts on this subject based on the ideXlab platform.

  • first principles study of crystal face specificity in surface properties of fe rich fe cr alloys
    Physical Review Materials, 2019
    Co-Authors: Stephan Schonecker, Levente Vitos, Borje Johansson, Shengzhi Hao, Jijun Zhao
    Abstract:

    A density-functional theory investigation of the (100) and (110) surfaces of the Body-Centered Cubic (bcc) Fe1-xbCrxb binary alloys, x(b) <= 15 at.%, is reported. The energies and segregation en ...

  • longitudinal spin fluctuation contribution to thermal lattice expansion of paramagnetic fe
    Physical Review B, 2017
    Co-Authors: Zhihua Dong, Stephan Schonecker, Dengfu Chen, Mujun Long, Levente Vitos
    Abstract:

    Using an efficient first-principles computational scheme for paramagnetic Body-Centered Cubic (bcc) and face-centered Cubic (fcc) Fe, we investigate the impact of thermal longitudinal spin fluctuat ...

  • stability in bcc transition metals madelung and band energy effects due to alloying
    Physical Review Letters, 2009
    Co-Authors: A Landa, Levente Vitos, Per Soderlind, Andrei V Ruban, Oleg E Peil
    Abstract:

    The phase stability of group VB (V, Nb, and Ta) transition metals is explored by first-principles electronic-structure calculations. Alloying with a small amount of a neighboring metal can either stabilize or destabilize the Body-Centered-Cubic phase relative to low-symmetry rhombohedral phases. We show that band-structure effects determine phase stability when a particular group VB metal is alloyed with its nearest neighbors within the same d-transition series. In this case, the neighbor with less (to the left) and more (to the right) d electrons destabilize and stabilize bcc, respectively. When alloying with neighbors of higher d-transition series, electrostatic Madelung energy dominates and stabilizes the Body-Centered-Cubic phase. This surprising prediction invalidates current understanding of simple d-electron bonding that dictates high-symmetry Cubic and hexagonal phases.

  • body centered Cubic iron nickel alloy in earth s core
    Science, 2007
    Co-Authors: Leonid Dubrovinsky, Natalia Dubrovinskaia, O Narygina, I Kantor, A Kuznetzov, V B Prakapenka, Levente Vitos, Borje Johansson, A S Mikhaylushkin, S I Simak
    Abstract:

    Cosmochemical, geochemical, and geophysical studies provide evidence that Earth's core contains iron with substantial (5 to 15%) amounts of nickel. The iron-nickel alloy Fe0.9Ni0.1 has been studied in situ by means of angle-dispersive x-ray diffraction in internally heated diamond anvil cells (DACs), and its resistance has been measured as a function of pressure and temperature. At pressures above 225 gigapascals and temperatures over 3400 kelvin, Fe0.9Ni0.1 adopts a Body-Centered Cubic structure. Our experimental and theoretical results not only support the interpretation of shockwave data on pure iron as showing a solid-solid phase transition above about 200 gigapascals, but also suggest that iron alloys with geochemically reasonable compositions (that is, with substantial nickel, sulfur, or silicon content) adopt the bcc structure in Earth's inner core.

P Huang - One of the best experts on this subject based on the ideXlab platform.

  • depth dependent strain rate sensitivity and inverse indentation size effect of hardness in body centered Cubic nanocrystalline metals
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014
    Co-Authors: Jiyuan Zhao, Fei Wang, P Huang
    Abstract:

    Abstract Size effects on hardness ( H ) and strain rate sensitivity ( m ) of nanocrystalline (NC) Body-Centered Cubic Mo thin film were examined under nanoindentation testing. Contrast to existing reports that there was no indentation size effect on hardness in NC metals, inverse indentation size effect (ISE) in NC Mo was observed for the first time at penetration depths ranging from 15 to 200 nm, at all the loading strain rates applied. In addition, the strain rate sensitivity of NC Mo exhibited strong dependence on penetration depth, increasing dramatically with decreasing penetration depth. Surface effects related to two deformation mechanisms were proposed to be responsible for the observed inverse ISE on H and depth dependent m . Specifically, the mobility of screw dislocation/component and the diffusion length of interfacial diffusion were altered as the deformed region underneath the indenter was approaching the free surface, resulting in the unusual size effects in NC Mo.

  • grain size dependent strain rate sensitivity in nanocrystalline body centered Cubic metal thin films
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014
    Co-Authors: Qing Zhou, Jiyuan Zhao, J Y Xie, Fei Wang, P Huang
    Abstract:

    Abstract The strain rate sensitivity (m) and activation volume (v⁎) of three nanocrystalline (NC) Body-Centered Cubic (bcc) metals, i.e., W, Mo and Ta, with various grain sizes were evaluated by nanoindentation testing. Opposite to the conventional trend that NC bcc metals exhibit reduced m as the grain size was decreased, elevated m was observed as the grain size was reduced from ~90 nm to ~30 nm for all the samples concerned. It was proposed that the unusual variation trends of m for NC bcc metals were dominated by GB-related mechanisms when the grain size drops below a critical value.