QIAO Lijie LIU Rui XIAO Jimei University of Science and Technology Beijing
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Beijing
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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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Journal of Materials Research
Effects of stacking fault energy (SFE) on the thermal stability and mechanical properties of nanostructured (NS) Cu-Al alloys during thermal annealing were investigated in this study. Compared with NS Cu-5at.% Al alloy with the higher SFE, NS Cu-8at.% Al alloy exhibits the lower critical temperatures for the initiation of recrystallization and the transition from recovery-dominated to recrystallization-dominated process, which significantly signals its low thermal stability. This may be attributed to the large microstructural heterogeneities resulting from severe plastic deformation. With increasing the annealing temperatures, both Cu-Al alloys present the similar trend of decreased strength and improved ductility. Meanwhile, the remarkable enhancement of uniform elongation is achieved when the volume fraction of Static recrystallization (SRX) grains exceeds similar to 80%. Moreover, the better strength-ductility combination was achieved in the Cu-8at.% Al alloy with lower SFE.
关键词:
electron backscatter diffraction;dynamic plastic-deformation;aluminum;single-crystals;microstructural evolution;ultrahigh-strength;grain-refinement;shear bands;copper;recrystallization;ductility
Communications in Theoretical Physics
Traditional ligand-field theory has to be improved by taking into account both "pure electronic" contribution and electron-phonon interaction one (including lattice-vibrational relaxation energy). By means of improved ligand-field theory, R-1, R-2, R-3', R-2', and R-1' lines, U band, ground-state zero-field-splitting (GSZFS) and ground-state g factors as well as thermal shifts of R-1 line and R-2 line of yAG:Cr3+ have been calculated. The results are in very good agreement with the experimental data. In contrast with ruby, the octahedron of ligand oxygen ions surrounding the central Cr3+ ion in YAG:Cr is compressed along the [111] direction. Thus, for YAG:Cr3+ and ruby, the splitting of t(2)(3) (4)A(2) (or t(2)(3) E-2) has opposite order, and the trigonal-field parameters of the two crystals have opposite signs. In thermal shifts of R-1 and R-2 lines of YAG:Cr3+, the temperature-dependent contributions due to EPI are dominant.
关键词:
improved ligand-field theory;electron-phonon interaction;Stokes shift;energy spectrum;thermal shift;g factor;yttrium-aluminum-garnet;pressure;cr3;temperature;state;ions
