E DONG and Guoxing LIU (Department of Material Science and Engineering
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Nanjing University of Science and Technology
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Nanjing
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210014
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China)(To whom correspondence should be addressed)
材料科学技术（英）
In order to improve the homogeneity of the pseudo-alloy W-Cu used in a certain ordnance component. the formation of solid solution of W-Cu system with a positive heat of mixing by mechanical alloying (MA) has been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM).transmission electron microscopy (TEM ) and differential thermal analysis (DTA). It was found that the supersaturated solid solution phase formed in the whole investigated composition range from W90Cu10 to W60Cu40 (at.-%). although the systern W-Cu exhibits a total immiscibility in both solid and liquid states, A systematic investigation on W70Cu30 showed that a solid solubility of Cu in W increased with the milling time. The Iattice parameters of phase W decreased with the increasing of the milling time and solute content of Cu. The thermal stability of the solid solution was studied by DTA. It was found that the decomposition of solid solution. the recovery and the growth of the grain occurred over 2 50℃. The driving force of the solid solution W-Cu system by MA mainly comes from high density of defects bV ball milling, which would enhance the free energy of the system. The solution process is diffusion-controlled
关键词:
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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