材料期刊网

HIGHTEMPERATURE LOWCYCLE FATIGUE BEHAVIOR OF NICKELBASED SUPERALLOY GH4049

Author L.J. Chen1 , 2) , G. Yao1) , Z.G. Wang1) and J.F. Tian1) 1) State Key Laboratory for Fatigue and Fracture of Materials , Institute of Metal Research , The Chinese Academy of Sciences , Shenyang 110015 , China2) Department of Metallic Material Engineering , Shenyang Polytechnic University , Shenyang 110021 , China Manuscript received 18 October 1998

金属学报(英文版)

The cyclic stress response and lowcycle fatigue life for wrought nickelbased superalloy GH4049 were investigated in the temperature range from 500 to 800 The relationship between the strain amplitude and the number of stress reversals was given. The behavior of cyclic hardening was observed for higher strain amplitudes at all testing temperatures and the lowcycle fatigue life generally decreased with increasing testing temperature for the same strain range. In addition, fracture surfaces of the fatigued samples were examined by using a scanning electron microscope.

关键词: superalloy , null , null

The role of twinning-detwinning on fatigue fracture morphology of Mg-3%Al-1%Zn alloy

Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing

Typical fracture morphology of Mg-3%Al-1%Zn (AZ31) alloy after low cycle fatigue was investigated using SEM and optical microscope. It is shown that prolific lamellar Structure in the crack initiation and Crack stable propagation zone mainly results from twinning,while dimple structure formed in the unstable crack propagation and final rupture zone is mainly due to slip. The formation mechanisms of corresponding morphologies are proposed based on twinning and detwinning processes during compressive and tensile loading half cycles, respectively, for this alloy. (C) 2008 Elsevier B.V. All rights reserved.

关键词: Magnesium alloy;Twinning and detwinning;Low cycle fatigue;Fracture;morphology;high-cycle fatigue;magnesium alloys;mechanical anisotropy;crack;growth;mg alloys;zn alloys;behavior;twins;al;ductility

Investigations of EPR g Factors and Rhombic Distortion for the Rhombic Cu2+ Centers in K2Zn1-x Cu (x) F-4 Crystals at Low Temperature

Applied Magnetic Resonance

The electron paramagnetic resonance g factors g (i) (i = x, y, z) of two rhombic Cu2+ centers, Cu2+(II) and Cu2+(III), in K2Zn1-x Cu (x) F-4 crystals found at low temperature are calculated from the complete diagonalization (of energy matrix) method based on the cluster approach. The calculations show that the ground state wave function of the two rhombically compressed Cu2+ centers is with a small admixture of . The rhombic distortions for both Cu2+ centers are obtained from the calculations. The results are discussed.

关键词: electron-paramagnetic-resonance;atomic screening constants;hyperfine;parameters;gyromagnetic factor;spin resonance;scf functions;field;copper(ii);dependence;spectra

Laboratory of Fatigue and Fracture for Materials(LFFM)

WA NG Zhongguang Professor , Director of the LFFM , Shenyang , 110015 , China.

材料科学技术（英文）

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Mixed valence state and electrical conductivity of La1-xSrxCrO3

Journal of Alloys and Compounds

La1-xSrxCrO3 (x=0.0 similar to 0.5) samples were prepared by the sol-gel method. The crystal structures of La1-xSrxCrO3 at room temperature all are of the othorhombic perovskite GdFeO3-type. XPS analysis indicates that chromium ions are in mixed valence state. The introduction of Sr2+ into the lattice is compensated by the oxidation from Cr3+ to Cr6+ With x increasing, the amount of Cr6+ increases. The presence of the Cr6- is one of the key factors that affect the electric conductivity of La1-xSrxCrO3. (C) 2000 Elsevier Science S.A. All rights reserved.

关键词: rare earth;perovskite La1-xSrxCrO3;high-temperature conductivity;interconnector;XPS

Study on valence state and electrical conductivity of La1-xCaxCrO3

Journal of Physics and Chemistry of Solids

La1-xCaxCrO3 (x = 0.0-0.5) samples were prepared by the sol-gel method. The sintering temperature of the samples can decrease to 1573 K. The crystal structures of La1-xCaxCrO3 at room temperature all are of the orthorhombic perovskite GdFeO3-type. XPS analysis indicates that the chromium ions are in a mixed valence state. The introduction of Ca2+ into the lattice is compensated by the oxidation of Cr3+ to Cr6+. With increasing x, the amount of Cr6+ increases. The presence of Cr6+ is one of the key factors affecting the electrical conductivity of La1-xCaxCrO3. (C) 2001 Published by Elsevier Science Ltd.

关键词: ceramics;photoelectron spectroscopy;electrical conductivity

EFFECT OF RARE EARTH ADDITIONS ON FRACTURE PROPERTIES OF 2.25Cr-1Mo STEELS

HONG Youshi Institute of Mechanics , Academia Sinica , Beijing , ChinaW.R.TYSON B.FAUCHER Physical Metallurgy Research Laboratories , CANMET , Ottawa , Canada HONG Youshi Institute of Me-chanics , Academia Sinica , Beijing 100080 China

金属学报(英文版)

The inclusion parameters,fracture surface morphology and void growth characteristics of ten- sile and fracture toughness specimens of 2.25Cr-1Mo steels with and without rare-earth (RE)additions have been investigated by quantitative metaltography(QTM),scanning elec- tron microscopy(SEM)and energy dispersive spectroscopy(EDS).There is a substantially higher density of inclusions in the RE-treated steel,which has lower values of fracture proper- ties including critical values of COD and J integral(δ_c and J_(IC)),fracture strain(ε_f) and Charpy V-notch energy(CVN).The fracture surface of the RE-treated steel comprises equiaxed dimples of diameters comparable with its inclusion spacing,whereas for the non-RE-treated steels,a wide range of dimple sizes is found with average diameter much smaller than the corresponding inclusion spacing.The investigation indicates that the lower values of fracture properties for the steel with RE at room temperature may be ascribed to its large content of RE-containing inclusions.

关键词: Cr-Mo steel , null , null , null

TEXTURES,INTERFACE AND FRACTURE OF A 1D-C/C PREPARED BY CVD

R.Shi , H.J. Li , Z. Yang and M.K. Kang(Dept. of Materials Science and Engineering , Northwestern Polytechnical University , Xi'an 710072 , China Manuscript received 26 August 1996)

金属学报(英文版)

A unidirectional carbon/carbon composite (1D-C/C) of low bulk density with textures of poruns granular and isotropic carbons sharply manifests brittle fracture and does not display high pseudoplasticity as expected. The results of transmisson electron microscopy (TEM) studies show that the strong interface of fiber-matrix should determine its fracture mode.

关键词: :1D-C/C , null , null , null

THERMAL FATIGUE AND FRACTURE MECHANICS ANALYSIS OF GREY CAST IRON

GUO Chengbi ZHOU Weisheng Dalian Institute of Technology , Dalian , Liaoning , China Professor , Dept.of Shipbuilding , Dalian Institute of Technology , Dalian , Liaoning , China

金属学报(英文版)

The in-phase and out-of-phase thermal fatigue,the C-P type and P-C type isothermal fa- tigue of grey cast iron were experimentally studied.The fatigue life was evaluated analytically by using the elastic-plastic fracture mechanics method(mainly J integral).The results of ex- periments and calculations showed that the lifes of in-phase and C-P type fatigue are longer than that of out-of-phase and P-C type fatigue respectively within the same strain range. This is in contrast to the results of other materials such as low carbon steel.On the other hand, the predicted lifes are consistent with experimental results.This suggests that J integral as a mechanics parameter for characterizing the thermal fatigue strength of grey cast iron and the mechanics model and the calculation method developed here are efficient.A parameter ΔW_1 was proposed from energy aspect to characterize the capacity of crack propagation. The isothermal fatigue life is the same as the thermal fatigue life for identical ΔW_1 values.

关键词: grey cast iron , null , null

Preparation and Superconducting Properties of F-doped SmO_1-xF_xFeAs

Zhiyong Liu

材料科学技术（英文）

Here we report the fabrication and superconductivity of the iron-based arsenic oxide SmO_1-xF_xFeAs compound. X-ray diffraction (XRD) results prove that the lattice parameters a and c decrease systematically with increasing x in between 0<x≤0.35, but when x>0.35 the a and c increase with the decrease of x in
the SmO_1-xF_xFeAs. The critical temperature (T_c) increases with increasing x in between 0.15≤x≤0.3, while x>0.3 the T_c decreases with the increase of x. It is found that at x=0.3 SmO_0.7F_0.3FeAs has the highest onset resistivity transition temperature of 55.5 K. The critical current density (J_c) value at 10 K for the obtained SmO_0.7F_0.3FeAs is 1.3×10⁵ A/cm² (0 T). Meanwhile one can estimates H_c2(0) from the slope of the H_c2(T) curve at T=T_c (H_C2 is the upper critical field), and for the 90% normal-state resistivity (ρ_n) criterion (T_c=55 K), H_c2(0) is determined to be ~253 T.

关键词: SmO_1-xF_xFeAs compound