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CRACK GROWTH, FRACTURE FEATURE AND RUPTURE LIFEDURING CYCLIC CREEP OF SUPERALLOY GH2132

Author M.F. Geng1) , T. Wang1) and X.A. Zhang2) 1) Department of Special Metal Materials and Products , Luoyang Ship Material Research Institute , Luoyang 471039 , China2) Mechanical Properties Laboratory , Beijing Institute of Aeronautical Materials , Beijing 100095 , China Manuscript received18 October 1998

金属学报(英文版)

The effects of cyclic loading on crack growth, fracture feature and rupture life of superalloy GH2132 have been studied in the present paper. The crack growth tests were carried out at 550 on compact tension specimens under a wide range of load levels and various periods of hold time, and the fracture surfaces were examined on a scanning electron microscope. The results show that, for both static and cyclic creep, Stage-I of crack growth is related with initial test stress, during which the crack extension is about 0.5mm, and that the final effect of cyclic loading on rupture life depends on the counteraction of its two reversed effects on crack growth rate before and after the point n=0.2.

关键词: cyclic creep , null , null , null , null , null

Magnetic properties of 1T-TaS2

Chinese Physics Letters

The magnetic properties of 1 T-TaS2 and 1 T-Fe-0.07 Ta-0.93 S-2 have been studied, Experimental results show that the phase transition temperature of 1 T-TaS2 is a function of the magnetic field, At low temperatures, both compounds are in a mixed state of charge density wave -spin density wave due to the coherent superposition of antiferromagnetic coupling.

关键词: density

A Simplified Regular Solution Model for Solubility of Nonmetal (2) in Metal(1)-Metal(3) Alloy Systems

Zheng FANG(Dept. of Chemistry , Central South University of Technology , Changsha 410083 , China)Quanru ZHANG(Dept. of Metallurgy , Changsha Technical College , Changsha 410012 , China)

材料科学技术(英文)

A simplifled regular solution model for the solubility of nonmetallic element (2) in metal(1)-metal(3) alloy system has been derived and applied to the Fe-C-j, Ni-C-j and Fe-N-j (j denotes a metal) systems with satisfaction. The exchange energies of concerned systems are evaluated

关键词:

Adsorption of Na on Ge(001)(2 x 1) surface

Physica B-Condensed Matter

The adsorption of sodium on the Ge(0 0 1)(2 x 1) surface at the coverage (Theta) of 0.5 and 1 ML has been investigated by using ab initio total energy calculations. It was found that at Theta = 0.5 ML T3 and T4 sites are nearly degenerate and Na adatoms preferred to adsorb at T3 and T4 sites. This finding agrees well with Meyerheim et al.'s experimental results, but does not support theoretical investigations of Spiess et al., who found HH site was the most stable. For 1 ML coverage the most stable configurations are a combination of the HH and T3 or T4 sites. Work function and dipole moment analysis showed that upon Na adsorption on Ge(0 0 1)(2 x 1) and Si(0 0 1)(2 x 1) surface the dipole-dipole repulsion is small and no depolarization effect occurs as the coverage increases from 0.5 to I ML. (c) 2005 Elsevier B.V. All rights reserved.

关键词: sodium;germanium;adsorption;work function;ab initio;adsorbed si(100) surfaces;double-layer model;ab-initio;covered;si(100);2x1-k surface;2 x-1;states;cs;overlayer;oxidation

PHASE-TRANSITION AND ELECTRON LOCALIZATION IN 1T-TAS2

Physical Review B

The magnetic properties and phase transitions of 1T-TaS2 and 1T-Fe0.07Ta0.93S2 have been studied in the interval of 1.5-300 K and over the range of 100 Oe-60 kOe. Experimental results show that at high temperatures the compounds are in a diamagnetic state and the commensurate-charge-density-wave-triclinic-nearly-commensurate transition temperature of 1T-TaS2 decreases with increasing magnetic field. The amount of variation is a function of the magnetic field. At low temperatures both 1T-TaS2 and 1T-Fe0.07Ta0.93S2 are in a paramagnetic state owing to the localized moments that come from the single Anderson-Mott localization state. The curves of magnetization versus temperature do not follow the Curie law or Curie-Weiss law, but can be described fairly well as M = M(0) + gamma T--n. The fitting parameters of experimental curves show that a part of the neighboring moment appears as antiferromagnetic coupling due to exchange interaction between the moments. The magnetic-field dependence of magnetization exhibits a complicated feature at low temperature. It shows that the compounds may undergo a phase transition at the maximum value of magnetization and then they are probably in a mixed charge-density-wave-spin-density-wave (CDW-SDW) state or SDW state due to the coherent superposition of the antiferromagnetic coupling.

关键词: metal-insulator-transition;density-wave domains;high magnetic-fields;charge-density;doped 1t-tas2;coexistence;microscopy;systems;silicon;2h-tas2

Single crystal T(0.3)MoO(3) growth by electrolytic reduction method of a T1(2)CO(3)-MoO(3) melts

Journal of Crystal Growth

Single crystals of quasi-one-dimensional charge-density-wave conductor blue bronze Tl(0.3)MoO(3) have been grown by electrolytic reduction method using the raw materials Tl(2)CO(3)-MoO(3) with composition around 1:4.3 mol ration. The electrolytic temperature was about 570 degrees C, and electrolytic current was 25 mA during the electrolytic process. By this method, the Tl(0.3)MoO(3) single crystals obtained have a relatively large average size and high quality. Platelet crystals with typical dimensions of 7 x 2 x 1 mm(3) were obtained. The crystal structure is monoclinic with space group C2/m. The parameters of the unit cell of the single crystal are as follows: a = 18.486(6)angstrom, b = 7.555(2)angstrom, c = 10.032(3)angstrom and beta = 118.38(3)degrees. The C-center symmetry of Tl(0.3)MoO(3) crystal is demonstrated by the selected area electron diffraction (SAED) patterns in the transmission electron microscope (TEM). The full-width at half-maximum (FWHM) of the rocking curve of the (201) Bragg peak of the Tl(0.3)MoO(3) was approximately 0.4 degrees. These are evidences that the single crystal is of high quality. The temperature dependence of the resistivity shows that a metal-semiconductor transition occurs near 181 K. (c) 2005 Elsevier B.V. All rights reserved.

关键词: electrolytic reduction;single crystal growth;thallium blue bronze;Tl(0).(3)MoO(3);charge density wave;charge-density-wave;molybdenum oxide bronzes;blue bronze;nonlinear;transport;k0.3moo3;k0.30moo3;memory;dynamics;lithium;noise

Temperature dependence of elastic properties of Ni(2+x)Mn(1-x)Ga and Ni(2)Mn(Ga(1-x)Al(x)) from first principles

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

ANALYSIS OF DEPOSITED PRODUCTS AND REANODIZED POROUS LUBRICATING FILM ON A1 AFTER(NH_4)_2MoS_4 SOLUTION TREATMENT

JIANG Guang , WU Yinshun , LI Jiuqing , LIU Haiping University of Science and Technology Beijing , Beijing , China Department of Surface Sciences and Corrosion Engineering , University of Science and Technology Beijing , Beijing 100083 , China

金属学报(英文版)

Observation was carried out of the structure of sulphuric,oxalic or phosphoric film on Al after treatment of reanodizing and electrolytic depositing lubricant in (NH_4)_2MoS_4 solution,as well as of the deposited products by means of EMPA,TEM and energy spectro-scopic analysis.The deposited products are mixture of compounds of S and Mo rather than single MoS_2 and most of them dcposited near the surface layer of the film.Some regular long pores without barrier layer occurred in the film,but the regular fine channels without relation to the structural element parameters of original anodized film were found in the thickened barrier layer of phosphoric film.Sulphur may be remained as Mo sulphide in the film during heating under Ar protective environment.

关键词: Al , null , null , null , null

First-principle study of electronic properties of Ti3Si1-xAlxC2 solid solutions

Journal of Physics and Chemistry of Solids

The layered ternary ceramics Ti3SiC2 and Ti3AlC2 are isostructural and can form Ti3Si1-xAlxC2 solid solutions combining the advanced properties of both compounds [H.B. Zhang, Y.C. Zhou, Y.W. Bao, M.S. Li, Improving the oxidation resistance of Ti3SiC2 by forming a Ti3Si0.90Al0.1C2 solid solution, Acta Mater. 52 (2004) 3631-3637; E.D. Wu, J.Y. Wang, H.B. Zhang, Y.C. Zhou, K. Sun, Y.J. Xue, Neutron diffraction studies of Ti3Si0.9Al0.1C2 compound, Mater. Lett. 59 (2005) 2715-2719; J.Y. Wang, Y.C. Zhou, First-principles study of equilibrium properties and electronic structure of Ti3Si0.75Al0.25C2 solid solution, J. Phys.: Condens. Matter 15 (2003) 5959-5968; Y.C. Zhou, J.X. Chen, J.Y. Wang, Strengthening of Ti3AlC2 by incorporation of Si to form Ti3Al1-xSixC2 solid solutions, Acta. Mater. 54 (2006) 1317-1322]. In the present work, the solid solutions of Ti3Si1-xAlxC2 (x = 0, 0.25, 0.33, 0.5, 0.67, 0.75, 1) are investigated by first-principle calculations based on pseudo-potential plan-wave method within the density functional theory framework. The results show that as Al content increases in the solid solution, all the bonds have weakened to certain extents, which lead to an unstable structure both energetically and geometrically. The calculated results are compared and discussed with the reported data for the Ti3Si1-xAlxC2 solid solutions. (c) 2007 Elsevier Ltd. All rights reserved.

关键词: ceramics;ab initio calculations;electronic structure;electrical;conductivity;oxidation behavior;mechanical-properties;ti3sic2;temperature;ti3alc2;air;si

MAGNETIC PHASE DIAGRAM OF SmMn_2(Ge_(1-x)Si_x)_2 SYSTEM

Y.G. Wang , F.M Yang , C.P. Chen , N Tang , and Q.D. Wang (State Key Laboratory of Magnetism , Institute of Physics , Chinese Academy of Sciences , P.O. Box 603 , Beijing 100080 , China)(Department of Materials Science and Engineering , Zheiang University Hangzhou 310027 , China)

金属学报(英文版)

The magnetic phase diagram (x,T) of the SmMn2(Ge1-xSix)2 system has been studied by susceptibility and magnetization measurement. With increasing silicon concentration the temperature region of ferromagnetic ordering decreases on the phaae diagram.

关键词: magnetic phase diagram , null , null , null

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