XU Yongbo HA Kuanfu WANG Zhongguang YANG Chunsong DAI Zhongling Laboratory for Fatigue and Fracture of Materials
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Institute of Metal Research
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Academia Sinica
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Shenyang
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110015
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China.Jilin University
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Changchun
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130023
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China.To whom correspondence should be add
材料科学技术（英）
An investigation has been made of the disloca- tion distribution and dislocation free zone near the crack tip in bulk Fe-3% Si single crystal during deformation in SEM.It has been found that a number of dislocations were emitted from the crack tip during deformation.After that,the dislocations moved rapidly away from the crack tip,which indi- cated that they were strongly repelled by the stress field at the crack tip.Between the crack tip and the plastic zone there is a region of dislocation-free, which is referred to as dislocation-free zone (DFZ). The length of DFZs is roughly estimated 100 μm which is much longer than that found in thin foil specimen.The variation of dislocation density as a function of the distance from the crack tip was measured,which showed that the dislocations are inversely piled up in the plastic zone.The length of DFZs increased with both the length of pre-crack and the amplitude of applied stress.
关键词:
dislocation
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Haibo LI Weitao ZHENG Yudong LIU Ruilin ZHANG Department of Materials Science
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Jilin University
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Changchun
,
130023
,
China
材料科学技术（英）
The procedure of preparing specimens of ultrafine particles (UFP) Fe_3O_4 was studied and the measurement and analysis of the Mssbauer spectra at room temperature was made.After the hyperfine field due to iron was analyzed carefully,it is shown that the interaction of the interfaces be- tween grains of UFP Fe_3O_4 has stronger effects (enlarging the quadrupole splitting in Mssbauer spectrum) and it is found that superparamagnetic effects appear,which means that the magnetic property of UFP Fe_3O_4 is different from that of bulk Fe_3O_4.
关键词:
UFP
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