QIAO Lijie LIU Rui XIAO Jimei University of Science and Technology Beijing
,
Beijing
,
China
金属学报(英文版)
The effects of stress components on nucleation sites and propagation directions of stress cor- rosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. The results indicated that under mode Ⅱ loading,stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendieular to the maximum normal stress,under mode Ⅲ loading,the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentra- tion,while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10—150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.
关键词:
stress corrosion cracking
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null
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null
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null
J.H. Yang and T.H. Zhang(Nantong Institute of Technology
,
Nantong 226007
,
China)(Radiation Beam and Materials Engineering Lab
,
Beijing Normal University
,
Beijing 100875
,
China)
金属学报(英文版)
Ta and C ions extracted from a MEVVA ion source were implanted into Cr12 steel, with an implantation dose of (1-5)x1017cm-2, extraction acceleration 42kV, and average ion beam flux about 20-50μA·cm-2. Rutherford backscattering spectrum (RBS) was used to measure the surface composition after Ta and Ta+C implantation. Analysis of phase formed by Ta and C implantation was carried out by X-ray diffraction analysis (XRD). Experiment results showed that the wear rate of the implanted layer dropped 40% for Ta ion implantation and by a factor of 2.7 for Ta+C dual ion implantation. Ta+C dual ion implantation was found to reduce the friction coefficient of Cr12 steel. The wear mechanisms of the implanted layer were discussed.
关键词:
wear resistance
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null
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null
S.Q. Duan
,
S.J. Liu and B.K. Ma(Department of Physics
,
Beijing Normal University
,
Beijing 100875
,
China)
金属学报(英文版)
Electronic structure calculations using the tighting-binding linear muffin-tin orbital (TB-LMTO) method have been performed for Co3Ti and its hydride CO3Ti. The computed values of lattice constants and bulk moduli agree with the experiment values. The theoritical excess enerpy and lattice staid due to hydrogen absorption consequently obtained hem the ab initio results indicate that H has the tendency to stay in Co3Ti and the ionicities of Co atomic spheres due to hydmpen absorption change from the canons to the ations. On the other hand, the changes of band structures due to hydrogenation are found to be remarkable.
关键词:
total enerpy
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null
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null
Y.T. Liu
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X.J. Guan
,
X.M. Shen
,
X.F. Ma
,
L.J.Wang
,
null
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null
,
null
,
null
金属学报(英文版)
The microstructures and their kinetics of normal
grain growth are simulated using different Monte Carlo (MC)
algorithms. Compared with the relative figures and the theoretical
normal grain growth exponents of n=0.5, the effects of some
factors of MC algorithm, i.e. the lattice types, the methods of
selecting lattice sites, and the neighbors selection for energy
calculations, on the simulation results of grain growth are studied.
Two methods of regression were compared, and the three-parameter
nonlinear regression is much more suitable for fitting the grain
growth kinetics. A better model with appropriate factors included
triangular lattice, the attempted site randomly selected, and the
first and second nearest neighbors for energy calculations is
obtained.
关键词:
Grain growth
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null
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null
Materials Letters
beta-quartz, stable at room temperature and under normal pressure, is obtained by high-pressure quenching, using an all-silicon ZSM-5 zeolite as the reaction precursor and characterized by means of X-ray diffraction.
关键词:
Science and Engineering of Composite Materials
The impact toughness of normal bamboo, reformed bamboo and reformed bamboo reinforced composites was studied comparatively by using a computerized Automatic Impact Testing System. It is found that the impact toughness of normal bamboo is dependent on the direction of the impact load. If the impact load is applied in the radial direction of the bamboo culm, the specimen impacted on the pith-ring has a much higher impact toughness than those impacted on the rind side. The impact toughness of reformed bamboo is somewhat lower than that of normal bamboo when most static mechanical properties are increased. The experimental results reveal that one of the technical parameters of reformed bamboo, the compressive ratio, is closely related to its impact toughness. However, the composition of reformed bamboo with glass fabric and aluminum sheets can improve the impact properties of reformed bamboo composites to a satisfactory extent while maintaining the superiority of their static mechanical properties.
关键词:
reformed bamboo;impact toughness;dynamic fracture
Applied Physics Letters
The magnetocaloric effect (MCE) at the antiferromagnetic (AF) to ferromagnetic (F) phase transition in Mn1.05Ni0.85Ge and CrO1.86F0.14, and the MCE at the F-AF transition in Tb3Co have been investigated. Mn1.05Ni0.85Ge and CrO1.86F0.14 are found to exhibit the inverse MCE whereas the MCE of Tb3Co is normal. For these compounds, the dependence of the transition temperature on the applied magnetic field B has been studied. A thermodynamical analysis is presented of the sign of the magnetic-entropy change in these three compounds which are representatives of two different types of B-T diagrams. Other possible B-T diagrams are discussed and the analysis is extended to AF-F and F-AF phase transitions reported in literature. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729122]
关键词:
Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms
Evolutions of angular distributions and surface composition profiles of a sputtered Pt0.5Cu0.5 alloy were simulated under 1 keV Ar ion bombardment at normal incidence, with the help of a dynamic Monte Carlo program including preferential sputtering and BIGS (bombardment-induced Gibbsian segregation) processes etc. It is found during the PtCu alloy sputtering that the Cu enrichment in the near-normal direction is regularly transformed into the Pt one as the Ar ion fluence increases. Below a low fluence of about 1.7 ions/cm2, Cu is preferentially ejected in the near-normal direction; above 1.7 ions/cm2, on the other hand, Pt is preferentially ejected in the near-normal direction instead of Cu. Effects of preferential sputtering and BIGS processes on enrichment transformation between Cu and Pt elements in the near-normal direction are also discussed.
关键词:
bombardment-induced segregation;monte-carlo simulation;surface;segregation;cu;implantation;depth
