Xiuying GAI Jiabao LI Zengqiao KANG State Key Lab.for Fatigue and Fracture of Materials
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Institute of Metal Research
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Academia Sinica
,
Shenyang
,
110015
,
ChinaJiawen HE Xi'an Jiaotong University
,
Xi'an
,
710049
,
China
材料科学技术（英）
Surface yielding of metallic material was measured with strain gage and X-ray diffraction methods. The results show that.when the residual stress in the transverse direction is involved,the surface yield strength should be evaluated with biaxial Mises criterion.For a medium carbon high strength steel, the yield strength of the bulk material is 581 MPa and the surface yield strengths for 0.05% and 0.1%plastic strain are about 436 MPa and 463 MPa respectively.The 0.05% yield strength will approximately increase to 788 MPa after shot peening.In the early stage of plastic deformation, strain hardening in the surface layer is quite different from that of the bulk sample.
关键词:
biaxial stress
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null
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null
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WU Shanghua LIU Yumen Materials Science Institute
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Zhongshan University
,
Guangzhou
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510275
,
China.Department of Materials Science and Engineering
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Xi'an Jiaotong University
,
Xi'an
,
710049
,
China.To whom correspondence should be addressed.
材料科学技术（英）
The martensitic transformation in Fe-Cr-W-V-C alloy has been investigated by TEM.The habit plane of martensite is near (252)_f, the austenite/martensite orientation relationship is Kurdjumov-Sachs'.In the martensite plates there are twins on (112)[ 1]_b,dislocation tangles and the lattice defects on (011)_b plane.In the austenite near the growing martensite plates,the dislocations with high density and stacking faults can be observed. The substructure of martensite may probably be the result of accommodation deformation during martensitic transformations.
关键词:
martensite
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Kewei XU Jiawen HE Huijiu ZHOU Research Institute for Strength of Metals
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Xi'an Jiaotong University
,
Xi'an
,
710049
,
China
材料科学技术（英）
The measurement of internal stresses in a PACVD TiN film proved experimentally to be difficult by a conventional X-ray diffraction technique.The linear relationship between 2θ and sin~2(?) could hardly be reached in some cases.Nevertheless.a good confirmation between the variation of FWHM-sin~2(?) and 20-sin~2(?) was revealed for every nonlinear forms.It followed that the effect of nondistributed micro-strains might exist in plasma assisted vapor deposited films,which usually have a strong crystal orientation,and the method of effectively separating macro-stress and micro-strain must be applied for the precise determination of internal stresses in PACVD films.
关键词:
TiN film
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null
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Huifen CHAI Zheng RUAN Quncheng FAN Dept.of Materials Science and Engineering
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Xi'an Jiaotong University
,
Xi'an
,
710049
,
China
材料科学技术（英）
The prestrained metals show substantial asymmetry between tension and compression in addition to the softening under cyclic loading, thus the cyclic creep takes place at a load-control test. The soft- ening reflects the decrease in density of dislocation and total internal stress, and the creep implies the asymmetry in back stress between tension and compression, The mechanical behaviour of the soft- ening is similar for materials with different slip modes, but their features of creep differ significantly. The creep of planar slip Cu-Zn alloy exhibits“explosively”, while that of wavy slip Cu and low car- bon steel occurs continuously and slowly. The explanation of creep behaviour via the internal dislo- cation structure was presented in this paper. According to asymmetw behaviour, it can be concluded that the internal processes of softehing also strongly depend on the slip mode. In addition, under high stress amplitude the opposite asymmetries take place for Cu and Cu-Zn alloy, it indicates that asymmetric back stresses developed in pretension have been eliminated even though the density and the configuration of dislocations have not reached equilibrium.
关键词:
internal stress
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