The Experts below are selected from a list of 40494 Experts worldwide ranked by ideXlab platform
Taketo Sakuma - One of the best experts on this subject based on the ideXlab platform.
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Vacancy effect of dopant cation on the high-Temperature Creep resistance in polycrystalline Al2O3
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, Taketo SakumaAbstract:Abstract High-Temperature Creep resistance in polycrystalline Al2O3 with 0.1 mol% oxides of YO1.5, ZrO2 or MgO has been examined by uniaxial compression Creep testing at 1250 °C. The Creep resistance is highly improved by the doping of Y or Zr even in the dopant level of 0.1 mol%, but is retarded by Mg doping. The dopant effect on the Creep resistance cannot be explained in terms of, for example, ionic radius of the dopant cation or eutectic point in Al2O3-oxide of dopant cation system. Each dopant cation was found to segregate in grain boundaries, and is likely to influence grain boundary diffusion in Al2O3. The ionic bonding and the covalent bonding of Al–O are lowered by the introduction of VO′′ or VAl′′′ but the values of the net charge in Al and O are increased by the cations doping. The change in the value of Net Charge is correlated well with the high-Temperature Creep resistance in Al2O3 with cation doping. It is suggested that the ionicity in Al and O is an important factor to determine high-Temperature Creep resistance in polycrystalline Al2O3.
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high Temperature Creep resistance in rare earth doped fine grained al2o3
Journal of Materials Research, 1998Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, Taketo SakumaAbstract:High-Temperature Creep in undoped Al 2 O 3 and La 2 O 3 - or Y 2 O 3 - or Lu 2 O 3 -doped Al 2 O 3 with a grain size of about 1 µm is examined in uniaxial compression testing at Temperatures between 1150 and 1350 °C. The high-Temperature Creep resistance in Al 2 O 3 is highly improved by the rare-earth oxide doping in the level of 0.045 mol %, and the Creep rate is suppressed in the order La 2 O 3 2 O 3 2 O 3 . Rare-earth ions in each doped Al 2 O 3 are found to segregate in Al 2 O 3 grain boundaries without forming amorphous phase or second-phase particles. The activation energy for Creep in undoped Al 2 O 3 is estimated to be 410 kJ/mol, while it is about 800 kJ/mol in the three rare-earth oxide-doped Al 2 O 3 . The grain boundary diffusivity must be highly reduced by the segregation of the dopant cation in Al 2 O 3 grain boundaries.
Shiqiang Deng - One of the best experts on this subject based on the ideXlab platform.
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High Temperature Creep behaviour of single crystal oxides
Journal of Materials Science, 1996Co-Authors: Shiqiang DengAbstract:The Creep resistance of several single crystal oxides is evaluated on the basis of Creep data from different sources using a Larson-Miller (L-M) method. The possible Creep mechanisms involved in high Temperature Creep deformation of single crystal oxides are discussed by comparing the collected Creep data with theoretical Creep models. The high Temperature Creep of single crystal oxides is generally considered as a diffusion-controlled process: dislocation climb controlled by the lattice diffusion of the slowest moving species (power law) at moderately high stresses, Harper-Dorn Creep at low stresses, and power law breakdown at high stresses. The relative comparison of the Creep data from different sources using the L-M method and the general analysis about the high Temperature Creep behaviour indicate that single crystal oxides with a precise stoichiometric composition, complex crystal structure and selected orientation such as [111] oriented YAG (Y3Al5O12),c-axis Al2O3, [110] oriented MgAl2O4 are potential candidates as reinforcements for very high Temperature structural applications.
Derek O. Northwood - One of the best experts on this subject based on the ideXlab platform.
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Room Temperature Creep of a high strength steel
Materials & Design, 2001Co-Authors: Cheng Liu, Ping Liu, Zhenbo Zhao, Derek O. NorthwoodAbstract:Abstract The time dependent deformation at room Temperature of a high strength steel was investigated. The room Temperature Creep tests showed that Creep can occur below 1/3 σ0.2 (yield strength at 0.2% offset). The resulting Creep behavior consists of only two stages, including primary Creep and steady-state Creep, each of which has its own distinctive strain–time features. The effects of Creep stress, Creep time, steel hardness and heat treatment schedule on the room Temperature Creep were investigated. It is believed that the increased Creep strains can be attributed to higher applied stresses, longer Creep times, lower hardnesses and the existence of an inhomogeneous microstructure. However, increasing the number of cycles in cyclic Creep tests at room Temperature resulted in a decrease in Creep strain. Possible room Temperature Creep mechanisms have been proposed and discussed.
Hidehiro Yoshida - One of the best experts on this subject based on the ideXlab platform.
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Vacancy effect of dopant cation on the high-Temperature Creep resistance in polycrystalline Al2O3
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, Taketo SakumaAbstract:Abstract High-Temperature Creep resistance in polycrystalline Al2O3 with 0.1 mol% oxides of YO1.5, ZrO2 or MgO has been examined by uniaxial compression Creep testing at 1250 °C. The Creep resistance is highly improved by the doping of Y or Zr even in the dopant level of 0.1 mol%, but is retarded by Mg doping. The dopant effect on the Creep resistance cannot be explained in terms of, for example, ionic radius of the dopant cation or eutectic point in Al2O3-oxide of dopant cation system. Each dopant cation was found to segregate in grain boundaries, and is likely to influence grain boundary diffusion in Al2O3. The ionic bonding and the covalent bonding of Al–O are lowered by the introduction of VO′′ or VAl′′′ but the values of the net charge in Al and O are increased by the cations doping. The change in the value of Net Charge is correlated well with the high-Temperature Creep resistance in Al2O3 with cation doping. It is suggested that the ionicity in Al and O is an important factor to determine high-Temperature Creep resistance in polycrystalline Al2O3.
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high Temperature Creep resistance in rare earth doped fine grained al2o3
Journal of Materials Research, 1998Co-Authors: Hidehiro Yoshida, Yuichi Ikuhara, Taketo SakumaAbstract:High-Temperature Creep in undoped Al 2 O 3 and La 2 O 3 - or Y 2 O 3 - or Lu 2 O 3 -doped Al 2 O 3 with a grain size of about 1 µm is examined in uniaxial compression testing at Temperatures between 1150 and 1350 °C. The high-Temperature Creep resistance in Al 2 O 3 is highly improved by the rare-earth oxide doping in the level of 0.045 mol %, and the Creep rate is suppressed in the order La 2 O 3 2 O 3 2 O 3 . Rare-earth ions in each doped Al 2 O 3 are found to segregate in Al 2 O 3 grain boundaries without forming amorphous phase or second-phase particles. The activation energy for Creep in undoped Al 2 O 3 is estimated to be 410 kJ/mol, while it is about 800 kJ/mol in the three rare-earth oxide-doped Al 2 O 3 . The grain boundary diffusivity must be highly reduced by the segregation of the dopant cation in Al 2 O 3 grain boundaries.
Jian Peng - One of the best experts on this subject based on the ideXlab platform.
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Room-Temperature Creep behavior on crack tip of commercially pure titanium
Materials & Design, 2015Co-Authors: Qiao Dai, Chang-yu Zhou, Jian PengAbstract:Abstract The room-Temperature Creep behavior on crack tip of compact tensile (CT) specimen for commercially pure titanium (CP-Ti) was studied by experiment and finite element (FE) simulation in this paper. The experimental results indicated that the time-dependent deformation was observed on the crack tip of CP-Ti CT specimen at room Temperature, which agreed with the primary Creep, and crack propagation was not observed. In order to consider the Creep behavior on crack tip, time-dependent J-integral was used to characterize the stress fields near crack tip. The room-Temperature Creep behavior on crack tip was analyzed by FE simulation, which was verified by experimental results. Then, the strain fields under different stress states were analyzed by FE simulation. The influences of the locations to crack tip and load on the room-Temperature Creep were analyzed, which shows that the Creep significance on crack tip is enhanced with increasing of load and decreasing of distance to crack tip. The estimation formula of Creep strain value along ligament direction of CP-Ti CT specimen was established and verified by FE simulation results.
