XU Yourong ZHANG Henghua CHEN Darning XIE Fuchun XU Mingyu Shanghai University of Science and Technology
,
Shanghai
,
ChinaCHEN Lanying SU Baorong QIAN Hongbin Shanghai Optics and Fine Mechinery Research Institute
,
Academia Sinica
,
Shanghai
,
China XU Yourong
,
professor
,
Department of Materials Science and Engineering
,
Shanghai University of Science and Technology
,
Shanghai 201800
,
China
金属学报(英文版)
Effect of laser scanning speed on phase constitution,microstructure,microhardness and wear resistance of laser-cladding hard facing alloy Stellite 12 has been investigated by means of a cross-flow-type CO_2 laser of 1.5 kW.The laser-cladding layer on the alloy consists of ma- trix phase of suppersaturated solid solution γ(Co,Cr)and complex hexagonal carbide M_7C_3.Under certain condition,at higher laser scanning speed,the suppersaturated solubility of elements increases in γ(Co,Cr),and the precipitation of the complex carbtde M_7C_3 de- creases,so the microhardness increases and the wear resistance decreases.But at slower laser scanning speed,more complex carbide M_7C_3 may precipitate,and the wear resistance may be improved.Therefore,it is believed that the principal factor in improving wear resistance is the precipitation of carbide M_7C_3,while increment of microhardness is the suppersaturated solu- bility of elements in matrix phase γ(Co,Cr).
关键词:
laser-cladding
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null
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null
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ZHANG Yuanhu SUN Jian XIANG Yi HU Gengxiang Shanghai Jiaotong University
,
Shanghai
,
ChinaLI Tiefan Institute of Corrosion and Protection of Metals
,
Academia Sinica
,
Shenyang
,
China Yuanhu
,
Department of Materials Science and Engineering
,
Shanghai Jiaotong University
,
Shanghai
,
200030
金属学报(英文版)
Studies on the high temperature creep and fracture behaviours in air or in SO_2 contaminated environment for the Fe-base superalloy GH302 with flat or zigzag grain boundaries(GB) and the Ni-base superalloy Rene 80 were carried out.Although the creep rupture properties of the GH302 with zigzag GB was remarkably superior to that of flat GB in air,the properties of both droped dramatically in 10% SO_2-air environment,the creep rupture properties of the directional solidified Rene 80 were much better than that of the conventionally cast alloy in air,and also kept the same property in SO_2 contaminated environment as in air.Owing to the interaction between creep and sulphidation,the failure mechanism relates to the formation of molten Ni-Ni-3S_2 eutectic along GB,led to the premature failure of the alloy.
关键词:
superalloy
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null
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null
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null
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DENG Yongrui University of Science and Technology Beijing
,
Beijing
,
ChinaG.S.Ansell Colorado School of Mines
,
Golden
,
CO 80401
,
USA) Associate professor
,
Department of Materials Science and Engineering
,
University of Science and Technology Beijing
,
Beijing 100083
,
China.
金属学报(英文版)
The growth of thermoelastic martensite in a Cu-29% Zn-3% Al alloy has been investigated experimentally and theoretically.Metallographie observations showed that the growth oc- cured thermoelastically,i.e.reversibly,in the radial direction as well as in the thickening di- rection.This is not consistent with the theories of Conhen and some others.A model has been suggested to explain the thermoelasticity of the growth.The basic idea is:the elastic strain distribution is highly heterogeneous and the growth is controlled by the local elastic strain en- ergy at the growth frontier area.The calculated results from the model based on Eshelby's theory are consistent with the observations.
关键词:
thermoelasticity
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null
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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
,
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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null
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null
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SHI Deke LIU Junhai Xi'an Jiaotong University
,
Xi'an
,
China SHI Deke
,
Associate Professor
,
Department of Materials Science and Engineering
,
Xi'an Jiaotong University
,
Xi'an
,
China
金属学报(英文版)
The work hardening of Hadfield manganese steel arises mainly form two causes;1)a large amount of twinning makes perfect dislocations or Shockley dislocations to be blocked at the coherent twin boundaries.2)the deformation leads to strong unsymmetrical distortion due to the occurrence of a large number gf Mn-C pairs or Mn-vacancy carbon-carbon cluster.It has been demonstrated by TEM observation and internal friction tests.As deformation pro- ceeds,the slip constantly accomodates twinning shear giving rise to stress relaxation.Thus, the Hadfield steel exhibits both rapid work hardening and good ductility.
关键词:
twin
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null
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HE Jianhong TANG Xiangyun CHEN Nanping Tsinghua University
,
Beijing
,
China Professor
,
Division of Metallic Meterials
,
Department of Materials Science and Engineering
,
Tsinghua University
,
Beijing
,
China
金属学报(英文版)
The permeation curves of hydrogen in ferritic-austenitic duplex stainless steel have been electrochemically determined.The apparent diffusivity of hydrogen depends on the austenite content(f_γ)at room temperature,D=(0.27+0.9/f_γ~2)(10~(-10)cm~2/s).It is simply verified that hydrogen in ferritic-austenitic duplex stainless steel diffuses in “series-connection” form through both ferrite grain and austenite grain.The apparent diffusivity is D=D_αD_γ/(f_α~2D_γ+f_γ~2D_α),where D_α,D_γ are diffusivity of hydrogen in ferrite grain and austenite grain respectively,f_α,f_γ are volume fraction,in turn,of ferrite grain and austenite grain.
关键词:
hydrogen
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null
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HU Guangli LIU Zhengtang WANG Ping HUA Wenjun KANG Mokuang Northwestern Polytechnical University
,
Xi'an
,
China HU Guangli
,
Associate Professor
,
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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null
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DONG jianxin XIE Xishan ZHANG Shouhua University of Science and Technology Beijing
,
Beijing
,
China doctorate student
,
Department of Materials Science and Engineering
,
University of Science and Technology Beijing
,
Beijing 100083
,
China
金属学报(英文版)
The precipitation behavior in Inconel 718 and modified alloys has been studied by means of TEM.The structure of associated precipitation and compact morphology of γ″+γ′ were ob- tained by modifying the contents of Al,Ti and Nb.Experimental results show that the com- pact morphology of γ″+γ′ has the best structure stability at higher temperatures.Instead of the transformation γ″→δ in alloy 718 the dissolution of strengthening phases in modified alloy leads material degradation.
关键词:
superalloy
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null
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null
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null
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null
YANG Guobin GUAN Zhiqun WANG Shuangquan WANG Run Beijing University of Science and Technology
,
Beijing
,
China Professor
,
Department of Materials Science and Engineering
,
Beijing Univ.of Science and Technology
,
Beijing
,
China
金属学报(英文版)
An inflection hehaviour was revealed during isothermal annealing under the observation of transition of the coercivity of Fe-Si-B amorphous alloys during local crystallization.It may be interpreted by the transition of α-Fe grain precipitated from single to multiple domain, Thus,the theoretical expression of H_0-t_a may be derived.The plot of expression H_0-t_a calcu- lated well represents the feature of the experimental curve.
关键词:
Fe-base amorphous alloy
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null
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JIANG Hai TAO Kun LI Hengde Tsinghua University
,
Beijing
,
China lecturer
,
Department of Materials Science and Engineering
,
Tsinghua University
,
Beijing 100084
,
China
金属学报(英文版)
BN films,synthesized by ion beam assisted deposition,were analysed by RBS,AES, IR spectra and TEM.Formatiom of c-BN phase was shown not only by IR spectra at absorption peak of 1100 cm~(-1),but also by electron diffraction pattern.The results of AES demonstrate an effect of N~+ implantation near the film surface.The deposited films consist of three layers,i.e.,ion implantation layer,film layer and mixed intermediatelayer, according to the difference of concentration.The micro-Knoop hardness of the film is 25—35 GPa.
关键词:
ion beam assisted deposition
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