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
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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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LI Jianguo MAO Xiemin FU Hengzhi National Laboratory of solidification Technology
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Northwestern Polytechnical University
,
Xi'an
,
China Lecturer.Faculty No.403
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Northwestern Polytechnical University
,
Xi'an 710072
,
China
金属学报(英文版)
The interface morphologies and microstruetures of the directionally solidified Ni-5wt-% Cu alloy during dendrite-to-cell transition at high growth rates have been investigated with a newly developed apparatus for unidirectional solidification with the temperature gradient at the solid/liquid interface higher than 1000 K/cm.The results show that in the vicinity of dendrite-to-cell transition point,the well developed sidebranches become shrivelled with the increase of growth rate and disappear at the dendrite-to-cell transition,and the primary spacing decreases simultaneously.Moreover,the length of mushy zone decreases greatly dur- ing the dendrite-to-cell transition.Cells obtained at high growth rates have very similar morphologies to those at low growth rates,but with much smaller cell spacings and unsmoothed cell walls which may be attributed to the different stability conditions of the cell walls at low and high growth rates respectively.
关键词:
cellular growth
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ZHOU Yigang YU Hanqing ZENG Weidong Northwestern Polytechnical University
,
Xi'an
,
ChinaTANG Jialin China South Aviation Motive Power and Machinery Company
,
Zhuzhou
,
China professor
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Department of Materials Science and Engineering
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China
金属学报(英文版)
Effect of β-flecks on properties of tensile elongation and low cycle.fatigue life at room tern. perature for Ti-10V-2Fe-3Al alloy has been investigated.The cracks along initial β-grain boundaries in the β-fleck region may propagate to form intergranular brittle fracture.Under alternating load,the β-fleck often becomes a fatigue origin.While under higher strain,the cracks initiate and propagate to fracture early at the original β-grain boundaries in β-fleck region and at α-grain boundaries.
关键词:
Ti-10V-2Fe-3Al alloy
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YANG Yanqing MA Shiliang QIN Xiongpu KANG Mokuang Northwestern Polytechnical University
,
Xi'an
,
China YANG Yanqing
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Graduate student
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Dept.of Materials Science and Engineering
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China
金属学报(英文版)
Two types of lath structures and kinked ε martensite were observed in the high manganese non-magnetic steel.Both the short non-continuous lath formed by quenching and the long thin straight lath induced by plastic deformation are composed of ε martensite and fcc twin. The transformation mechanism was discussed.The crystallographic analysis indicates that the e martensite at both sides of the fcc twin boundary is of kinked morphology owing to the orientation of their matrices differing from each other.The kinked region is hcp twin.
关键词:
εmartensite
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HU Guangli LIU Zhengtang WANG Ping HUA Wenjun KANG Mokuang Northwestern Polytechnical University
,
Xi'an
,
China HU Guangli
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Associate Professor
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Department of Materials Science and Engineering
,
Northwestern Polytechnical University
,
Xi'an
,
China
金属学报(英文版)
The variations of microstructures and mechanical properties of steels 15CrMnMoV, 18Mn2CrMoB,18Cr2Ni4W,30CrMnSi,30CrMnSiNi2 and 40CrMnSiMoV,which were tempered at different temperatures after austempering and continuous cooling at given rates, have been investigated.Based on the experimental results,the behaviour and mechanism of tempered bainite embrittlement(TBE)have been discussed.Finally,the theoretical and prac- tical basis for selecting the optimum tempering temperature of steels with bainite structure af- ter heat treatment are proposed.
关键词:
austempering
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LIU Junming ZHOU Yaohe SHANG Baolu Northwestern Polytechnical University
,
Xi'an
,
China LIU Junming P.O.Box No.219
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China
金属学报(英文版)
Nonstable growth of Al-Si eutectic in constrained condition has been investigated by means of change of the withdrawing rate in an unidirectional solidification system,In constant acceleration growth,a retarded effect of response of eutectic interflake spacing on the growth rate has been observed.The response mechanisms are cluster-branching and local termination extension of Si-phase.In constant deceleration growth,the cluster-branching and termina- tion mechanisms of silicon still control adjustment of the interflake spacing,but the spacing is determined by the initial growth rate and does not respond to the decreasing growth rate.
关键词:
Al-Si eutectic
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TIAN Changsheng WANG Minsheng HOU Tiecui DANG Xin'an Northwestern Polytechnical University.Xi'an
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China Associate Professor
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Department of Materials Science and Engineering
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China
金属学报(英文版)
In Situ observation of deformation and fracture for superalloy GH169 under combined fatigue-creep action is made by using high temperature metalloscope,it is shown that under the test conditions the deformution takes place by merely of slipping,twinning and grain houndary sliding,and the mode of failure depends on the microstructure of specimen. lntergranular cracks arise.from W-type voids produced by the stress concentration at triple point which could not be relaxed by the interior deformation of grains and the local deformathm region along grain bounaries.And the crack propagation mechanism is the nucleation,growth and linkage of carities at the grain boundaries.Transgranular cracks form from deformatiom damages within the grain,and its propagation mechanism is shear rupture along the slip phme.
关键词:
combined fatigue-creep action
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LIU Xiao ZHANG Mingxing CHEN Daming ZHOU Lubin KANG Mokuang Northwestern Polytechnical University
,
Xi'an
,
China LIU Xiao Faculty No.401
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Northwestern Polytechnical University
,
Xi'an 710072
,
China
金属学报(英文版)
CCT-diagrams of Si-Mn-Mo bainitic steels have been determined.With Mo 0.25%,the high-temperature transformation of the steel shifts large to the right,and the bainitic trans- formation region becomes a“flat topped C-curve”at cooling rate in wide range.Si in the steel may cause shift of the bainitic transformation region towards the right,and of the pro-eutectoid ferritic transformation region towards the left.Mn may delay the high temper- ature transformation more violently than the bainitic transformation.
关键词:
meta-bainite
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JIE Wanqi ZHOU Yaohe Northwestern Polytechnical University
,
Xi'an
,
China JIE Wanqi Department of Materials Science and Technology
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Northwestern Polytechnical University
,
Xi'an
,
China
金属学报(英文版)
Convection and constitution variation of liquid metal during solidification has been studied us- ing NH_4Cl aqueous solution.The liquid in mushy zone attached to the side wall of the mold will flow upward and form a low concentration region,in which no significant convection oc- curs,on the top of liquid zone.This region develops downward gradually during solidification. Addition of adequate component may suppress the formation of this region.
关键词:
liquid zone
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