Author X.A. Zhang1)
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H.Q. Xia1)
,
Z.T. Wu1)
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Y.F. Han1)
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R. Shi2) and G.X. Hu2) \= 1) Mechanical Properties Laboratory
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Beijing Institute of Aeronautical Materials
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Beijing 100095
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China2) The State Education Commission Open Research Laboratory for High Temperature
金属学报(英文版)
Materials and Testing, Shanghai Jiao Tong University, Shanghai 200030, ChinaManuscript received 18 October 1998 The threestage creep behavior of DD3 single crystal superalloy had been studied. The results show that the creeprupture properties of DD3 single crystal satisfy the requirements for high performance turbine blade application. The influence of crystal orientation on the creeprupture property of DD3 single crystal was tested and discussed. An engineering criterion to evaluate the regimes of secondary and tertiary creep is proposed, and this method gives a reasonable result for practical applications. The fractography and TEM micrography of the tested specimens had been studied, and it is determined that the glidecontrolled creep is the basic creep mechanism of DD3 single crystal at intermediate temperature, but the thermally activated processes become dominant at higher temperature.
关键词:
threestage creep curve
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null
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null
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null
Journal of Alloys and Compounds
The influence of R substitution in (La1-xRx)(2)Co16Ti compounds (R=Sm, Nd; x=0.0-1.0) on structural and magnetic properties has been investigated. The lattice parameters of the (La1-xRx)(2)Co16Ti compounds decrease with increasing x in the range 0 less than or equal to x less than or equal to 1.0. With x increasing, the saturation magnetic moment increases for (La1-xNdx)(2)Co16Ti while remains unaffected for (La1-xSmx)(2)Co16Ti. The Curie temperature increases with increasing Sm or Nd substitution. The uniaxial magnetocrystalline anisotropy of (La1-xSmx)(2)Co16Ti becomes enhanced with increasing Sm substitution. The anisotropy of (La1-xNdx)(2)Co16Ti changes from easy-axis (x<0.4) to easy-plane anisotropy (x>0.4). (C) 2000 Elsevier Science S.A. All rights reserved.
关键词:
intermetallic compounds;ternary rare earth compounds;magnetization;magnetic anisotropy;crystal structure;magnetocrystalline anisotropy
Journal of Alloys and Compounds
Polycrystalline Nd(Mn(1-x)Fe(x))(2)Ge(2) (0 <= x <= 1) compounds have been prepared by arc-melting. X-ray powder diffraction analysis shows that all samples crystallize in the ThCr(2)Si(2)-type structure with the space group 14/mmm. The substitution of Fe for Mn results in decreases of the lattice constants a, c and the unit-cell volume V. Magnetic properties and magnetocaloric effect of the compounds Nd(Mn(0.9)Fe(0.1))(2)Ge(2) and Nd(Mn(0.8)Fe(0.2))(2)Ge(2) have been studied by magnetic measurements. A spin reorientation transition at about 188 K is observed for Nd(Mn(0.9)Fe(0.1))(2)Ge(2). The Nd(Mn(0.8)Fe(0.2))(2)Ge(2) compound shows more complicated magnetic behavior, which is characterized by four magnetic ordering states below room temperature. The maximum values of the magnetic entropy change are 2.35 and 1.84 J kg(-1) K(-1) for x = 0.1 and 0.2, respectively, under the applied field changing from 0 to 5T. The relative cooling powers of Nd(Mn(0.9)Fe(0.1))(2)Ge(2) and Nd(Mn(0.8)Fe(0.2))(2)Ge(2) are 145.9 and 133.8 J kg(-1) under an applied field change of 5T. (C) 2009 Elsevier B.V. All rights reserved.
关键词:
Metals and alloys;Magnetocaloric;X-ray diffraction;room-temperature applications;neutron-diffraction;phase-transitions;crystal-structure;solid-solution;refrigeration;silicides;mn;0-less-than-or-equal-to-x-less-than-or-equal-to-1;mnas1-xsbx
Chinese Physics B
X-ray powder diffraction, resistivity and magnetization studies have been performed on polycrystalline Nd(Fe(x)Mn(1-x))(2)Si(2) (0 <= x <= 1) compounds which crystallize in a ThCr(2)Si(2)-type structure with the space group 14/mmm. The field-cooled temperature dependence of the magnetization curves shows that, at low temperatures, NdFe(2)Si(2) is antiferromagnetic, while the other compounds show ferromagnetic behaviour. The substitution of Fe for Mn leads to a decrease in lattice parameters a, c and unit-cell volume V. The Curie temperature of the compounds first increases, reaches a maximum around x = 0.7, then decreases with Fe content. However, the saturation magnetization decreases monotonically with increasing Fe content. This Fe concentration dependent magnetization of Nd(Fe(x)Mn(1-x))(2)Si(2) compounds can be well explained by taking into account the complex effect on magnetic properties due to the substitution of Mn by Fe. The temperature's square dependence on electrical resistivity indicates that the curve of Nd(Fe(0.6)Mn(0.4))(2)Si(2) has a quasi-linear character above its Curie temperature, which is typical of simple metals.
关键词:
Nd(Fe(x)Mn(1-x))(2)Si(2);crystal structure;magnetic properties;resistivity;neutron-diffraction;rmn2ge2 compounds;solid-solution;silicides;0-less-than-or-equal-to-x-less-than-or-equal-to-1;behavior;ndfe2si2
YANG Jilian ZHANC Baisheng DINC Yongfan China Institute of Atomic Engergy
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Beijing
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ChinaYANG Yingchang ZHANG Xiaodong Peking University
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Beijing
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ChinaPAN Shuming General Research Institute for Non-Ferrous Metals
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Beijing
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China associate professor
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P.O.Box 275
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Branch No.30
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Beijing 102413
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China
金属学报(英文版)
The N occupying sites and magnetic structures in R_2Fe_(17)N_x(R=Y,Dy,Nd)are de- termined by neutron diffraction.The effects of the site occupation of N on magnetic properties are discussed primarily.
关键词:
neutron diffraction
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null
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null
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null
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null
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Journal of Physics-Condensed Matter
In this study, the transport and magnetic properties of electron-doped perovskites R(x)Ca(1-x)MnO(3) (R = La, Y and Ce) were investigated. As the R ion content increases, the crystal structure, resistivity, magnetoresistance, magnetization and related characteristic temperature of these systems all vary systematically. The data show that the variations in the electrical transport properties are mainly dependent on carrier concentration, whereas the magnetic properties of these systems are also dependent on crystal structure. When the carrier concentration exceeds a certain level, charge ordering occurs, leading to the localized electronic state and peaks in the magnetization curves. The magnetic transition temperature T(N) can be well described by crystal structural parameters, suggesting that crystal structure and magnetic properties are strongly coupled to each other.
关键词:
rare-earth manganates;phase-separation;colossal magnetoresistance;manganites;oxides;bandwidth;physics;camno3;ln
International Journal of Modern Physics B
The EPR g factors g(//) and g(perpendicular to) for the six-coordinated Cu2+(1) site in YBa2Cu3O6+x are theoretically investigated from the perturbation formulas for a 3d(9) ion in tetragonally elongated octahedra. The related tetragonal crystal-field parameters Ds and Dt are determined from the superposition model and the structural data for the Cu2+(1) site, by considering the effective elongation of the oxygen octahedron due to the Jahn-Teller effect of the Cu2+ cluster. Based on the calculations, the effective elongation (= 15%) of the ligand octahedron is obtained for the signals at 100K. As for the EPR signals at room temperature, the elongation declines to merely 4%, corresponding to the smaller anisotropy Delta g (=g(//) - g(perpendicular to)). The theoretical results for the g factors are in good agreement with the observed values, and the local tetragonal distortion due to the Jahn-Teller effect is discussed.
关键词:
crystal fields and spin hamiltonians;electron paramagnetic resonance;Cu2+;YBa2Cu3O6+x;single-crystals;yba2cu3o7-delta;evolution;esr
Physical Review B
The temperature dependence of the elastic properties of Ni(2+x)Mn(1-x)Ga and Ni(2)Mn(Ga(1-x)Al(x)) (x = 0.0, 0.1, and 0.2) random alloys are investigated by using the first-principles exact muffin-tin orbitals method. At 0 K, the calculated equilibrium parameters in both cubic L2(1) and nonmodulated tetragonal beta'''-Ni(2)MnGa are in good agreement with the available experimental data and other theoretical results. Separating the thermal effects into single electron excitation, volume expansion, phonon smearing, and magnetic terms, we find that phonon smearing gives the dominating positive tetragonal elastic constant (C') versus temperature (T) slope for the cubic phase. For Ni(2+x)Mn(1-x)Ga, the competition between the negative alloying effect (partial derivative C'/partial derivative x < 0) and the positive temperature effect (partial derivative C'/partial derivative T > 0) leads to nearly constant C'[x, T(M)(x)] at the martensitic transition temperature T(M)(x). For Ni(2)Mn(Ga(1-x)Al(x)), where both partial derivative C'/partial derivative x and partial derivative C'/partial derivative T are positive, however, due to the significantly decrease of T(M)(x), the critical C'[x, T(M)(x)] slightly decreases with Al doping. Furthermore, it is demonstrated that both the composition and the temperature dependence of C' are indispensable to get a reasonable theoretical T(M)(x).
关键词:
shape-memory alloys;ni-mn-ga;martensitic phase-transformation;potential model;heusler alloys;ni2mnga alloy;landau theory;approximation;transitions;disorder
Japanese Journal of Applied Physics Part 1-Regular Papers Brief Communications & Review Papers
The structures and dielectric properties of Pb(Fe1/2Nb1/2)(1-x)TixO3 (PFNT, x = 0.07 and 0.48) single crystals were investigated using a combination of temperature-dependent dielectric, X-ray diffraction (XRD), Raman, and X-ray absorption fine structure (XAFS) spectra. Detailed structure analyses reveal that the crystal structure of PFNT (x = 0.48) is single-phase tetragonal perovskite, whereas that of PFNT (x = 0.07) is a mixture of rhombohedral and tetragonal phases. The structural differences are found to have significant connections with the dielectric properties in the temperature range of 90-300 K. Both samples exhibit a frequency-dependent dielectric anomaly, arising primarily from the 3d electrons hopping between Fe2+ and Fe3+. The second dielectric anomaly, which is a weak frequency dispersion and observable only for PFNT (x = 0.07), was probably caused by a dipole glass behavior near the morphotropic phase boundary. (C) 2012 The Japan Society of Applied Physics
关键词:
iron;fe;ceramics;region;xanes
