The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Yoshihito Kawamura - One of the best experts on this subject based on the ideXlab platform.
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formation of 14h long period stacking Ordered Structure and profuse stacking faults in mg zn gd alloys during isothermal aging at high temperature
Acta Materialia, 2007Co-Authors: Michiaki Yamasaki, Minami Sasaki, Masahiko Nishijima, Kenji Hiraga, Yoshihito KawamuraAbstract:Abstract This paper proposes a time–temperature-transformation diagram of an Mg–Zn–Gd alloy. An Mg 97 Zn 1 Gd 2 (at.%) alloy shows different precipitation sequences at low, medium and high temperatures. Low-temperature aging at 623 K led to strengthening of the Mg–Zn–Gd alloy, owing to the formation of profuse stacking faults and 14H long period stacking Ordered Structure from the supersaturated α-Mg matrix, respectively.
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formation and mechanical properties of mg97zn1re2 alloys with long period stacking Ordered Structure
Materials Transactions, 2007Co-Authors: Yoshihito Kawamura, Michiaki YamasakiAbstract:We investigated the formation and mechanical properties of Mg 97 Zn 1 RE 2 alloys with long-period stacking Ordered (LPSO) Structures by examining RE = Y, La, Ce, Pr, Sm, Nd, Gd, Dy, Ho, Er, Tb, Tm and Yb. The LPSO phase developed for RE = Y, Dy, Ho, Er, Gd, Tb and Tm. LPSO Mg-Zn-RE alloys are either type I, in which the LPSO phase forms during solidification: Mg-Zn-Y, Mg-Zn-Dy, Mg-Zn-Ho, Mg-Zn-Er and Mg-Zn-Tm, or type II, in which the LPSO phase is nonexistent in as-cast ingots but precipitates with soaking at 773 K: Mg-Zn-Gd and Mg-Zn-Tb. The criteria for REs that form an LPSO phase in Mg-Zn-RE alloys are discussed. Mg-Zn-RE alloys with an LPSO phase, which were worked by hot extrusion, include high strength both at ambient and elevated temperatures, and good ductility. Their tensile yield strength, ultimate strength and elongation were 342-377 MPa, 372-410MPa and 3-9%, respectively at ambient temperature, and 292-310MPa, 322-345 MPa and 4-13% at 473 K. The LPSO Mg-Zn-RE alloys are promising candidates for lightweight structural materials.
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elevated temperature mg97y2cu1 alloy with long period Ordered Structure
Scripta Materialia, 2006Co-Authors: Yoshihito Kawamura, Takayuki Kasahara, Shogo Izumi, Michiaki YamasakiAbstract:Mg97Y2Cu1 (at.%) cast alloy has an 18R-type long period Ordered (LPO) Structure that forms coherently with the α-Mg matrix during casting. Hot working improved the mechanical properties of the LPO Mg97Y2Cu1 cast alloy. Hot-extruded LPO Mg97Y2 Cu1 alloy exhibited high tensile mechanical properties. The yield strength, tensile strength and elongation were 297 MPa, 377 MPa and 8.1%, respectively, at ambient temperature, and 273 MPa, 344 MPa and 16.3%, respectively, at 473 K.
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long period Ordered Structure in a high strength nanocrystalline mg 1 at zn 2 at y alloy studied by atomic resolution z contrast stem
Acta Materialia, 2002Co-Authors: Yoshihito Kawamura, Kouichi Hayashi, Akihisa InoueAbstract:The microStructure of a nanocrystalline Mg97Zn1Y2 (at%) bulk alloy prepared by warm extrusion of rapidly solidified powders has been investigated by a combination of techniques, such as conventional high-resolution transmission electron microscopy (HRTEM), atomic-resolution high-angle annular dark field scanning-TEM (HAADF-STEM) with Z-contrast and energy-dispersive X-ray spectroscopy (EDS) with a sub-nanometer electron probe. We show that a novel long-period Ordered Structure is formed in the alloy, whose unit cell is composed of six close-packed planes of the magnesium crystal with a stacking sequence of ABCBCB′ where A and B′ layers are significantly enriched by Zn and Y. The lattice is distorted from an ideal hexagonal lattice of 6H-type (ABCBCB), which is probably due to an asymmetry of the chemical order with respect to the 6H-type stacking order. The present results demonstrate that the additional elements of a few atomic percent to Mg lead to formation of a long-period chemical-Ordered as well as stacking-Ordered Structure, as directly revealed by a unique Z-contrast method.
Michiaki Yamasaki - One of the best experts on this subject based on the ideXlab platform.
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formation of 14h long period stacking Ordered Structure and profuse stacking faults in mg zn gd alloys during isothermal aging at high temperature
Acta Materialia, 2007Co-Authors: Michiaki Yamasaki, Minami Sasaki, Masahiko Nishijima, Kenji Hiraga, Yoshihito KawamuraAbstract:Abstract This paper proposes a time–temperature-transformation diagram of an Mg–Zn–Gd alloy. An Mg 97 Zn 1 Gd 2 (at.%) alloy shows different precipitation sequences at low, medium and high temperatures. Low-temperature aging at 623 K led to strengthening of the Mg–Zn–Gd alloy, owing to the formation of profuse stacking faults and 14H long period stacking Ordered Structure from the supersaturated α-Mg matrix, respectively.
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formation and mechanical properties of mg97zn1re2 alloys with long period stacking Ordered Structure
Materials Transactions, 2007Co-Authors: Yoshihito Kawamura, Michiaki YamasakiAbstract:We investigated the formation and mechanical properties of Mg 97 Zn 1 RE 2 alloys with long-period stacking Ordered (LPSO) Structures by examining RE = Y, La, Ce, Pr, Sm, Nd, Gd, Dy, Ho, Er, Tb, Tm and Yb. The LPSO phase developed for RE = Y, Dy, Ho, Er, Gd, Tb and Tm. LPSO Mg-Zn-RE alloys are either type I, in which the LPSO phase forms during solidification: Mg-Zn-Y, Mg-Zn-Dy, Mg-Zn-Ho, Mg-Zn-Er and Mg-Zn-Tm, or type II, in which the LPSO phase is nonexistent in as-cast ingots but precipitates with soaking at 773 K: Mg-Zn-Gd and Mg-Zn-Tb. The criteria for REs that form an LPSO phase in Mg-Zn-RE alloys are discussed. Mg-Zn-RE alloys with an LPSO phase, which were worked by hot extrusion, include high strength both at ambient and elevated temperatures, and good ductility. Their tensile yield strength, ultimate strength and elongation were 342-377 MPa, 372-410MPa and 3-9%, respectively at ambient temperature, and 292-310MPa, 322-345 MPa and 4-13% at 473 K. The LPSO Mg-Zn-RE alloys are promising candidates for lightweight structural materials.
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elevated temperature mg97y2cu1 alloy with long period Ordered Structure
Scripta Materialia, 2006Co-Authors: Yoshihito Kawamura, Takayuki Kasahara, Shogo Izumi, Michiaki YamasakiAbstract:Mg97Y2Cu1 (at.%) cast alloy has an 18R-type long period Ordered (LPO) Structure that forms coherently with the α-Mg matrix during casting. Hot working improved the mechanical properties of the LPO Mg97Y2Cu1 cast alloy. Hot-extruded LPO Mg97Y2 Cu1 alloy exhibited high tensile mechanical properties. The yield strength, tensile strength and elongation were 297 MPa, 377 MPa and 8.1%, respectively, at ambient temperature, and 273 MPa, 344 MPa and 16.3%, respectively, at 473 K.
Norbert Schell - One of the best experts on this subject based on the ideXlab platform.
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Anisotropic Plastic Behavior in an Extruded Long-Period Ordered Structure Mg90Y6.5Ni3.5 (at.%) Alloy
Crystals, 2020Co-Authors: Gerardo Garcés, Andreas Stark, Rafael Barea, Norbert SchellAbstract:The Mg90Y6.5Ni3.5 alloy composed almost completely of the Long-Period-Stacking-Ordered (LPSO) phase has been prepared by casting and extrusion at high temperature. An elongated microStructure is obtained where the LPSO phase with 18R crystal Structure is oriented with its basal plane parallel to the extrusion direction. Islands of α-magnesium are located between the LPSO grains. The mechanical properties of the alloy are highly anisotropic and depend on the stress sign as well as the relative orientation between the stress and the extrusion axes. The alloy is stronger when it is compressed along the extrusion direction. Under this configuration, the slip of dislocations in the basal plane is highly limited. However, the activation of kinking induces an increase in the plastic deformation. In the transversal extrusion direction, some grains deform by the activation of basal slip. The difference in the yield stress between the different stress configurations decreases with the increase in the test temperature. The evolution of internal strains obtained during in-situ compressive experiments reveals that tensile twinning is not activated in the LPSO phase.
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anisotropic plastic behavior in an extruded long period Ordered Structure mg90y6 5ni3 5 at alloy
Crystals, 2020Co-Authors: Gerardo Garcés, Andreas Stark, Rafael Barea, Norbert SchellAbstract:The Mg90Y6.5Ni3.5 alloy composed almost completely of the Long-Period-Stacking-Ordered (LPSO) phase has been prepared by casting and extrusion at high temperature. An elongated microStructure is obtained where the LPSO phase with 18R crystal Structure is oriented with its basal plane parallel to the extrusion direction. Islands of α-magnesium are located between the LPSO grains. The mechanical properties of the alloy are highly anisotropic and depend on the stress sign as well as the relative orientation between the stress and the extrusion axes. The alloy is stronger when it is compressed along the extrusion direction. Under this configuration, the slip of dislocations in the basal plane is highly limited. However, the activation of kinking induces an increase in the plastic deformation. In the transversal extrusion direction, some grains deform by the activation of basal slip. The difference in the yield stress between the different stress configurations decreases with the increase in the test temperature. The evolution of internal strains obtained during in-situ compressive experiments reveals that tensile twinning is not activated in the LPSO phase.
Michael A Hayward - One of the best experts on this subject based on the ideXlab platform.
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the synthesis and complex anion vacancy Ordered Structure of la0 33sr0 67mno2 42
ChemInform, 2011Co-Authors: Edward Dixon, Joke Hadermann, Michael A HaywardAbstract:La0.33Sr0.67MnO3 is prepared by reaction of a stoichiometric mixture of La2O3, SrCO3, and MnO2 (argon stream; 1.
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the synthesis and complex anion vacancy Ordered Structure of la0 33sr0 67mno2 42
Journal of Solid State Chemistry, 2011Co-Authors: Edward Dixon, Joke Hadermann, Michael A HaywardAbstract:The low-temperature topotactic reduction of La{sub 0.33}Sr{sub 0.67}MnO{sub 3} with NaH results in the formation of La{sub 0.33}Sr{sub 0.67}MnO{sub 2.42}. A combination of neutron powder and electron diffraction data show that La{sub 0.33}Sr{sub 0.67}MnO{sub 2.42} adopts a novel anion-vacancy Ordered Structure with a 6-layer OOTOOT' stacking sequence of the 'octahedral' and tetrahedral layers (Pcmb, a=5.5804(1) A, b=23.4104(7) A, c=11.2441(3) A). A significant concentration of anion vacancies at the anion site, which links neighbouring 'octahedral' layers means that only 25% of the 'octahedral' manganese coordination sites actually have 6-fold MnO{sub 6} coordination, the remainder being MnO{sub 5} square-based pyramidal sites. The chains of cooperatively twisted apex-linked MnO{sub 4} tetrahedra adopt an Ordered -L-R-L-R- arrangement within each tetrahedral layer. This is the first published example of a fully refined Structure of this type which exhibits such intralayer ordering of the twisted tetrahedral chains. The rationale behind the contrasting Structures of La{sub 0.33}Sr{sub 0.67}MnO{sub 2.42} and other previously reported reduced La{sub 1-x}Sr{sub x}MnO{sub 3-y} phases is discussed. - Graphical Abstract: The topotactic reduction of the perovskite phase La{sub 0.33}Sr{sub 0.67}MnO{sub 3} with NaH yields La{sub 0.33}Sr{sub 0.67}MnO{sub 2.42(3)}, which adopts a novel anion vacancy Ordered Structure with a 6-layer OOTOOT' stacking sequence ofmore » the 'octahedral' and tetrahedral layers. The anion site that links the neighbouring octahedral layers is partially occupied so only 25% of the 'octahedral' manganese sites actually have 6-fold MnO{sub 6} coordination. Highlights: > Topotactic reduction with NaH to form a mixed valent Mn{sup 2+}/Mn{sup 3+} phase. > Novel layered anion-vacancy Ordered Structure. > Comparison to related brownmillerite Structure types.« less
Harushige Tsubakino - One of the best experts on this subject based on the ideXlab platform.
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novel equilibrium two phase mg alloy with the long period Ordered Structure
Scripta Materialia, 2004Co-Authors: Yasumasa Chino, Mamoru Mabuchi, Shigehiro Hagiwara, Hajime Iwasaki, Atsushi Yamamoto, Harushige TsubakinoAbstract:Abstract Mg–8at%Y–4at%Zn alloy is processed via a conventional casting method. The TEM images show the long-period Ordered Structure with six layered atomic packing in the matrix region of the cast ingot. High elastic modulus and hardness are attained due to the long-period Ordered Structure as a result of indentation tests.
