Z. Bian
,
G. He and G.L. Chen (State Key Laboratory for Advanced Metals and Materials
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University of Science and Technology Beijing
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Beijing 100083
,
China) J. Lu
,
D.J. Chen
,
G.C. Tu
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G.J. Chen and X.J. Hu (Shougang Metallurgical Research Institute
,
Beijing 100085
,
China)
金属学报(英文版)
Al80Ni6 Y8 Co4 Cu2 amorphous ribbons were isothermally annealed and a mixed structure consisting of α-Al particle with a size of less than 15nm and Al3Ni compound with a size of about 30nm was obtained. The crystallization kinetics of Al80Ni6 Y8 Co4 Cu2 amorphous alloy shows that the precipitation of α-Al particles is the growth process controlled by diffusion of the solute elements rejected from the growing crystals. By quenching at different cooling rates, a mixed structure consisting of nanoscale α-Al particles and the remaining glass matrix or structure consisting of nanoscale particle (Al phase or Al3Ni compound) with a size of about 100nm was formed. The addition of Co elements and Cu elements to Al-Ni-Y alloy systems increases the glass formation ability of the alloy and the thermal stability of the supercooled liquid region against crystallization, which results from significant difference of atomic size, strong bonding nature among constituent elements and the low diffisivity of the solute elements due to the concentration gradient in the growing front of crystals.
关键词:
a mixed structure
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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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Materials and Corrosion-Werkstoffe Und Korrosion
Carbon steels were pre-corroded in atmospheres containing certain pollutants such as sulfur dioxide or hydrogen sulfide or nitrogen dioxide for certain period of time. Then the pre-corroded samples were further exposed at two central test stations in the country to evaluate the influence of pre-corrosion on the behavior of long-term atmospheric corrosion of carbon steel by gravimetric measurement and rust examinations with FT-IR and XRD. The results showed that the corrosion rates of every kind of carbon steel at Jiangjin station were two times higher than that at Beijing station. The influence of different pre-corrosion conditions on the long-term atmospheric corrosion of carbon steel was analyzed. It followed that the pre-corrosion conditions made the long-term atmospheric corrosion performance of three kinds of carbon steels different, but the differences were small. Among the three pollutants, NO2 showed the strongest influence to the process. As the exposure time was going on, all the samples corroded slowly at Beijing and Jiangjin stations.
关键词:
pollution parameters;prediction;outdoor;rust
