Y. G .Zhang
,
C. Q. Chen (Beijing University of Aeronautics and Astronautics
,
Beijing 100083
,
China)Q. Xu (Beijing Laboratory of Electron Microscopy
,
Chinese Academy of Sciences. Beijing
,
China)M. C. Chaturvedi (The University of Manitoba
,
Winnipeg
,
Manitoba
,
Canada R3T 2N2)
金属学报(英文版)
A two-phase TiAl-based alloy with fully lamellar structure has been deformed al room temperature and the deformed microstructures have been examined in dtails by optical microscopy(OM), scanning electron microscopy(SEM) and transmission electron microscopy(TEM) . Deformation mechanisms in the γ-TiAl phase has been defined and the role of grain boundaries in the deformation and fracture has been assessed Some of the mechanisms of interactions between twinning or gliding dislocations and three types of γ γ domain boundaries or γ α_2 interface in a lamellar grain have been identified and resistance of the various domain boundaries or the interface to the propagation of twinning has been evaluated
关键词:
:TiAl
,
null
,
null
,
null
Journal of Superconductivity and Novel Magnetism
The local structure and the g factors (g(x), g(y), and g(z)) of the Cu(2+) site in Y(2)BaCuO(5) are theoretically studied using the perturbation formulas of the g factors for a 3d(9) ion in orthorhombically elongated octahedra. The orthorhombic field parameters in these formulas are determined from the superposition model and the local geometry of the system. From the calculations, the oxygen octahedron is found to undergo the local elongation Delta Z (approximate to 0.05 angstrom) along c-axis and the relative bond length variation Delta X (approximate to 0.1 angstrom) along a- and b-axes, respectively. The calculated g factors based on the above local structure are in good agreement with the experimental data. The relationships between the anisotropies of the g factors and the low symmetrical (orthorhombic) distortions of the Cu(2+) site in Y(2)BaCuO(5) are discussed.
关键词:
Crystal fields and spin Hamiltonians;Electron paramagnetic resonance;Cu(2+);Y(2)BaCuO(5);crystal
于萍
,
王亚权
腐蚀科学与防护技术
研究了添加0.1mass%稀土Y的铸造K38G高温合金在1000℃的恒温氧化行为.结果表明,较之不含Y的合金，含Y铸态K38G合金的氧化速率显著降低； 氧化时形成双层的外氧化膜，表层为以Cr2O3和TiO.2为主的混合氧化物层，内层为连续的Al2O3层；没有内氧化和内氮化，没有氧化膜的剥落，加入稀土Y有效地提高了氧化膜的粘附性能.
关键词:
高温氧化
,
null
,
null
,
null
于萍
,
王亚权
腐蚀科学与防护技术
doi:10.3969/j.issn.1002-6495.2007.03.010
研究了添加0.1 mass%稀土Y的铸造K38G高温合金在1000℃的恒温氧化行为.结果表明,较之不含Y的合金,含Y铸态K38G合金的氧化速率显著降低;氧化时形成双层的外氧化膜,表层为以Cr2O3和TiO2为主的混合氧化物层,内层为连续的Al2O3层;没有内氧化和内氮化,没有氧化膜的剥落,加入稀土Y有效地提高了氧化膜的粘附性能.
关键词:
高温氧化
,
K38G
,
高温合金
,
稀土元素
,
Y
于萍
,
王亚权
,
王文
腐蚀科学与防护技术
对加入0.05mass%～0.5mass%稀土Y铸造的K38G高温合金800 ℃恒温的氧化行为进行了研究.结果表明,含Y铸态K38G合金的氧化动力学曲线偏离了抛物线规律，接近于立方规律；Y有效抑制了该合金的内氧化；当Y含量达0.5mass%时，该合金中析出富Y相，降低了其氧化抗力.
关键词:
高温氧化
,
null
,
null
Physica Status Solidi B-Basic Research
The perturbation formulas of EPR g factors g(\\) g(perpendicular to) and hyperfine structure constants A(\\) A(perpendicular to) for the trigonal octahedral 3d(7) cluster are derived considering not only the configuration interaction effect due to the admixture among ground and excited states, but also the covalency effect due to the admixture between the d electrons of the 3d(7) ion and the p electrons of ligands. In these formulas, the parameters related to both effects and the trigonal field parameters are estimated from the optical spectra and the structural parameters of the studied system. According to these formulas, the EPR parameters g(\\), g(perpendicular to), A(\\) and A(perpendicular to) for Co2+ in the octahedral sites of Y3Al5O12 and Y3Ga5O12 garnets are satisfactorily explained from the optical spectra and the structure data. The role of the covalency effect is discussed.
关键词:
superposition model;phase-transition;absorption;linbo3;ions
