DONG Hongbiao JI Yongyi ZHU Jun LU Shuzu ZHONG Xueyou University of Science and Technology
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Beijing
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ChinaLI Jianguo Northwestern Polytechnical University
,
Xi'an
,
China DONG Hongbiao
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lecturer
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Department of Metallurgy
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University of Science and Technology Beijing
,
Beijing 100083
,
China
金属学报(英文版)
In situ eutectic Al_(11)La_3/Al composite material with regular arrangement was prepared by zone melt liquid metal cooling directionally solidification under conditions of high temperature gradient G=700K/cm and growth rate R=6.0-20.0μm/s.Superpose diffraction pat- tern of Al_(11)La_3/Al composite shows that the preferred growth direction is[100]Al// [33]Al_(11)La_3,and the habit plane is(002)Al//(116)Al_(11)La_3.A low density(103)twin is ob- served in Al_(11)La_3 and the growth of(103)twin induces to branching to change the interlamellar spacing.
关键词:
eutectic solidification
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SUN Jian ZHANG Yuanhu HU Gengxiang Shanghai Jiaotong University
,
Shanghai
,
China SUN Jian
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lecturer
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Department of Materials Science
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Shanghai Jiaotong University
,
Shanghai 200030
,
China
金属学报(英文版)
The creep crack propagation in superalloy René80 of two different microstructures,i.e., equiaxed grain structure by conventional casting and columnar grain by directional solidification,was investigated under static load at 1123 K.The creep crack growth rate, da/dt,seems to be correlated with the stress intensity factor,K.The creep crack growth rate in the directionally solidified alloy is lower than that in the conventional cast alloy,owing to the elimination of transverse grain boundaries.The effect of microstructure on creep crack propagation has also been discussed.
关键词:
Superalloy René 80
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LIU Shan LU Deyang HUANG Tao ZHOU Yaohe National Lab of Solidification Processing
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Northwestern Polytechnical University
,
Xi'an
,
China LIU Shan
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lecturer
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National Laboratory of Solidification Processing
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China
金属学报(英文版)
An experimental apparatus,which has a convection generator and an aid-heater,is developed for the study of the effect of stable laminar liquid flow on the directional solidification process by the use of transparent alloy SCN-2wt-% Ace.The flow is perpendicular to primary arms. By in-situ observation and photographing at different specific moments,it has been found that such a flow can cause a great change in primary spacings of constrained columnar crystals:for cells,the spacings become smaller;but for dendrites,they become larger.The former is mainly due to the tilted growth of upstreamside branches,while the latter is mainly due to the coup- ling effect of liquid flow with solutal field around dendrite tips.The faster the liquid flows,the further smaller the cell spacing and the further larger the dendrite spacing.
关键词:
forced liquid flow
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LIU Junming LIU Zhiguo WU Zhuangchun Nanjing University
,
China LIU Junming
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lecturer
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National Laboratory of Solid State Microstructuros
,
Nanjing University
,
Nanjing 210008
,
China
金属学报(英文版)
The profile features of the solidifying interface of the irregular Al-Si eutectic during directional solidification are studied by numerically solving a nonlinear coupling equation of directional solidification of this eutectic.The critical splitting point of the solidifying interface coincides with the maximum value of its position and corresponds to the marginal stability point.Argument is presented that the interlamellar spacing for local regular structure selects the critical splitting state of the α(Al)-liquid interface as its operating point,and the oper- ating point of the average interflake spacing for the irregular structure is the critical splitting state of the β(Si)-liquid interface.The scaling laws derived,which have the more general forms than the classic Jackson-Hunt scaling,gained support from the experimental results.
关键词:
irregular Al-Si eutectic
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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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