ZHOU Shouzeng TANG Weizhong WANG Run University of Science and Technology Beijing
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Beijing
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China
金属学报(英文版)
The boundary microstructure of sintered alloy Nd_(15.5)Fe_(77)B_-(7.5) has been studied by TEM,AES and SAED.The boundary structure may be distinguished into 4 types.The first three types remain the same during annealing,and the fourth changes its microstructure remarkably.The 4th type is composed of two different regions,i.e.,the central Nd-rich phase and the epitaxial laver of the Nd_2Fe_(14)B grains.Owing to the atomic diffusion and other types of mass trans- port,magnetic hardening occurred in the epitaxial layer,thus the coercivity of the alloy has been improved.
关键词:
NdFeB magnet
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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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